The Messenger

No. 171 – March 2018 La Silla Paranal instrumentation – a retrospective instrumentation Paranal La Silla roadmap The VLTI Primary Mirror ELT’s The ALMA with Sun the Exploring Telescopes and Instrumentation DOI: 10.18727/0722-6691/5061

40+ of Instrumentation for the La Silla

Sandro D’Odorico1 b. a Schmidt telescope with an aperture Germany. Two instrumentation groups, of about 1.20 metres; one optical and one infrared, were set up. c. not more than three telescopes with a They were led by astronomers who 1 ESO maximum aperture of 1 metre; reported directly to the Director General. d. a meridian circle; A dedicated group of engineers was put e. the auxiliary equipment needed to to work on the procurement and testing As ESO Period 100 comes to a close, carry out research programmes with of optical and infrared detectors and I look back at the development of ESO’s the instruments listed in a., b., c. and their control systems within the Technical instrumentation programme over more d. above…”. Division. A committee of astronomers than 40 years. Instrumentation and from the member countries and from detector activities were initially started When reading this text for the first time, ESO, later called the Scientific Technical by a small group of designers, engi- I was amused to see that only the Committee, provided the guidelines and neers, technicians and astronomers ­telescopes and the meridian circle only general specifications for these new while ESO was still at CERN in Geneva granted the title of “research instruments” developments. During those early years, in the late 1970s. They have since led to while everything else was more modestly when ESO began to build its reputation, the development of a successful suite described as “auxiliary equipment”. The the overall structure was agile and flexible of optical and infrared instruments for first telescopes erected at the La Silla and ensured that strategic choices in the the La Silla Paranal Observatory, as site (with diameters of 50 cm, 1 m and development of instruments were driven testified by the continuous growth in the 1.52 m) were equipped with “auxiliary by the science. number of proposals for observing time equipment” supplied by institutes in the and in the publications based on data member countries: photometers for the The importance of instrumentation and from ESO telescopes. The instrumenta- smaller telescopes and high-resolution the associated detectors to observational tion programme evolved significantly spectrographs for the 1.52-metre tele- astronomy cannot be underestimated. with the VLT and most instruments were scope. These instruments mostly dupli- Instruments serve as a key interface developed by national institutes in close cated similar ones in operation at Euro- between an observatory and its scientific cooperation with ESO. This policy was a pean sites and were conceived to carry users. Along with good atmospheric cornerstone of the VLT programme from out stellar work in the southern hemi- ­conditions and telescopes that operate the beginning and a key to its success. sphere, reflecting the focus of European smoothly, instrumentation can determine astronomy at that time. the scientific success of an observing run. If the instruments operate well and can Instrumentation: the interface between This was in the early 1970s, when the compete with those available elsewhere, ESO and its users North American observatories were astronomers will obtain high-quality data increasingly starting to focus their scien- that ultimately gives them a more effective Most astronomers in Europe are familiar tific research on extragalactic targets, long-term impact in their field of research. with ESO as it is today, with its three spurred on by the discovery of the first This, in short, is the primary goal of an observing sites in Chile, the Extremely quasars, which changed our view observatory. Large Telescope under construction, the of the Universe. European astronomy scientific and administrative centre in needed larger telescopes and modern Santiago, headquarters in Garching, and instru­mentation to compete with these 1978–1998: two decades of “fast and as the European partner in the Atacama exciting scientific developments. ESO’s furious” growth Large Millimeter/submillimeter Array founders had a vision that this was best (ALMA). However, they may not be aware achieved by joining forces, but progress The instrumentation and detector pro- of the modest goals (as compared to was initially slow. gramme started to show results at the tele­ today’s achievements) set by ESO’s scopes in Chile at the end of the 1970s. founders in the ESO Convention of 1962, The 3.6-metre telescope, ESO’s main First, the Coudé Échelle Spectrograph which was signed by representatives from project, saw first light in 1976. Lodewijk (CES) with a 1D digital detector become Belgium, France, the Federal Republic of Woltjer, ESO Director General from operational in the coudé room of the 3.6- Germany, the Netherlands and Sweden. 1975 to 1987, writes in his book (Woltjer, metre telescope, fed by the newly erected An excerpt from the English version of the 2006), “When I came to ESO in 1975, it 1.4-metre Coudé Auxiliary Telescope document states1, “The purpose of the was evident­ that there was no real plan (CAT) and, a few years later, by an optical Organisation shall be to build, fit out and to effectively use the 3.6 m telescope for fibre from the 3.6-metre. An off-the-shelf operate an astronomical observatory situ- contemporary science. There also would instrument, the Boller and Chivens grat- ated in the southern hemisphere. The be no suitable instrumentation to attach ing spectrograph, was acquired to offer ­initial programme of the Organisation to the telescope.” An instrumentation the possibility to observe faint objects at shall comprise the construction, installa- development programme was started the 3.6-metre. It initially used a 1D Image tion and operation of an observatory in while ESO was still at CERN in Geneva Dissector Scanner (IDS) detector. the southern hemisphere, consisting of: (between 1972 and 1980). This was further a. a telescope with an aperture of about expanded when the Organisation moved Two instruments designed and built by 3 metres; to its new Headquarters in Garching, ESO then become operational in 1984

2 The Messenger 171 – March 2018 Figure 1. Below is the hand-drawn map of the from the beginning of the 1980s, before the installation of the 2.2-metre telescope and the NTT. A photo from the same was taken from the plane that was used to commute staff from Santiago to the Pelicano airstrip close to La Silla. The small plane was in use until the early 1990s.

definition of several instruments (EMMI, FORS, UVES, X-shooter), which was always a gratifying experience. On receiv- ing a set of requirements, such as wave- length range, spectroscopic resolution, image scale and the likely properties of the detector, he would create a prelimi- nary, often original, design in just a few days. A robust discussion with the pro- ject team would follow, about perfor- mance, feasibility and cost, and would eventually lead to a final configuration that formed part of an instrument proposal.

Table 1 lists the most-demanded instru- ments at the three most powerful La Silla telescopes, along with their period of operation and the number of publications that have used their data. The years from 1978 to 1998 saw a spectacular growth in ESO facilities, with the arrival of new instruments at the 3.6-metre telescope, the installation of the 2.2-metre Max- Planck-Gesellschaft (MPG)/ESO tele­ scope and the completion of the (NTT) with three fixed instruments at its two Nasmyth foci. All of this was during the construction of the VLT. The growing interest and con- fidence of the community in the use of ESO’s facilities was reflected in the num- ber of observing proposals, which went from about 150 in 1978 to over 550 in and 1985: CASPEC, an efficient cross- EFOSC deserves a special mention. This 1995 (Patat et al., 2017). dispersed échelle spectrograph and the innovative transmission optics instrument ESO Faint Object Spectrograph & Cam- was the first major work by the ESO The use of near-infrared (NIR) instruments era (EFOSC). Both used silicon charge- designer Bernard Delabre, who recently was initially limited by the lack of suitable coupled device (CCD) detectors — the retired. It was followed by an upgraded detectors. In the first part of this period, first to operate at the 3.6-metre tele- version, EFOSC2, which served as the the first NIR spectrograph, IRSPEC, scope. The high efficiency of the optics, prototype for the very successful FORS started operating at the 3.6-metre tele- coupled with the high quantum sensitivity instruments at the scope with just a 32-diode linear detector, of the CCDs, boosted the performance (VLT). As noted by de Zeeuw et al. (2017), which was upgraded to a 58 × 62 pixel of these instruments and, for the first EFOSC clones or derivatives have been InSb array when the instrument was time, gave European astronomers the built for telescopes distributed across moved to the NTT in 1991. A few years possibility of competing on crucial observ- almost all continents. Delabre put for­- later when the 1k × 1k pixel HgCdTe ing modes with their colleagues at other ward many other original ideas over his infrared arrays become available, ESO 4-metre-class telescopes worldwide. 40 years at ESO, with the consistent aim quickly put them into operation using two In the mid-1980s these two instruments of designing more efficient instruments new instruments, SOFI at the NTT and regularly used around 60 % of the tele- using affordable optics. Most VLT instru- ISAAC at the VLT. The two were immedi- scope nights. ments are based on his designs or incor- ately in high demand and delivered a rich porate his ideas. I worked with him on the harvest of scientific results.

The Messenger 171 – March 2018 3 Telescopes and Instrumentation D’Odorico S., 40+ Years of Instrumentation for the La Silla Paranal Observatory

Instrument name Acronym Telescope Instrument type Operating time No. papers Bollers & Chivens B & C 3.6 m Grating spectrograph 1978–1990 N/A Cassegrain Échelle Spectrograph CASPEC 3.6 m Échelle spectrograph + spectropolarimetric mode 1984–1999 N/A ESO Faint Object Spectrograph and Camera 1–2a EFOSC1–2 3.6 m, NTT Spectrograph, imager, polarimeter 1985 —> 690 Infrared Spectrometer IRSPEC 3.6 m, NTT NIR 1D spectrograph 1987–1996 N/A Thermal Infrared Multi-Mode Instrumentb TIMMI2 3.6 m MIR spectrograph & imager 2000–2006 97 High Accuracy Planet ­Searcherb HARPS 3.6 m Échelle spectrograph 2 0 0 3 —> 689 ESO Multi-Mode Instrument EMMI NTT Spectrograph & imager 1990–2008 689 Son of ISAAC SOFI NTT NIR spectrograph & imager 1 9 9 8 —> 809 SUperb Seeing Instrument 2 SUSI2 NTT Imager 1998–2008 130 Wide Field Imagerb WFI 2.2 md Wide field imager 1998–2013 515 Fibre-fed Extended Range Optical Spectrograph­ b, c FEROS 2.2 md Échelle spectrograph 2003–2013 676

Table 1. The most popular instruments at the largest What I have outlined in this article is a challenges of large telescopes; the La Silla telescopes. The publication statistics are somewhat selective version of two dec- favourable economic situation in ESO from 1 January 2000 to 31 January 2018, and are therefore unavailable for some of the earliest instru- ades of the history of instrumentation Member States; and the growing interest ments. Some of the instruments were built by con- at the La Silla Observatory. Other tele- within the scientific community and sortia; please see the Notes at the end of the article scopes, the ESO 1-metre Schmidt, which amongst the public about new astronom- for ­further information on the Principal Investigators was dedicated to the southern sky photo­ ical discoveries from the ground and from and teams. graphic survey, the spectroscopic ESO space. The good results obtained with 1.52-metre and the Danish 1.54-metre the first ESO-built instruments, like CES, with its CCD camera (the first to be CASPEC and EFOSC, also helped to While the ESO-built instruments took installed on La Silla) and later host to the build confidence in ESO in the scientific up the bulk of the observing time at the Danish version of EFOSC, also contrib- community and in members of the ESO 3.6-metre telescope and at the NTT, the uted significantly to the scientific growth Council. telescopes were also used by visitor of the user community. Additional instru- instruments or part-time instruments sup- ments served a large number of users Discussions about VLT instrumentation plied by national institutes. Most notably, well; for example, the prime focus cam- started very early in the project, with VLT the three adaptive optics (AO) systems eras and OCTOPUS (a multi fibre Working Groups, focused on different (Come-On, Come-On+ and the ADaptive spectro­graph at the 3.6-metre telescope), observing modes and composed of Optics Near Infrared System [ADONIS]) the two Boller & Chivens spectrographs external and ESO scientists, set up in and a mid-infrared (MIR) version of EFOSC at the 1.52-metre and the 2.2-metre 1985. After these interactions, the first called TIMMI (superseded by TIMMI2), ­telescopes, FEROS at the 1.52-metre version of the VLT instrumentation plan were developed in France and played a ­telescope, and infrared cameras IRAC was released in 1990 (D’Odorico et al., key role as scientific tools and as test and IRAC2 at the 2.2-metre telescope. 1991), more than 8 years before first light. benches for future VLT instruments. These were particularly useful in building It already contained an outline of the first the expertise that later bore fruit at the instruments to be built and the strategy Starting in 1993 at the NTT, a high-­ VLT. More details on various projects for their procurement. resolution NIR camera, SHARP (built in conducted over 50 years of ESO can be Germany), was used by a dedicated team found in Madsen (2012). The cornerstones of the proposed for observations of the Galactic Centre, approach, which was new for ground- opening up a very successful line of based observatories, were: research that has continued on to the The VLT era (1999–2018): collaborating – The majority of instruments had to be present day with the VLT instruments with ESO Member State institutes built by institutes, with ESO contribut- ­SINFONI and ­GRAVITY, the latter only ing standard items and selected commissioned in 2017. A later addition to Construction of the VLT was approved by subsystems. the list of instruments supplied by the ESO Council in December 1987. This – Instruments had to comply with a set of national institutes was the high-stability was well before NTT first light in March verifiable specifications and would be échelle spectrograph HARPS in 2003, 1989, so the exceptional image quality subject to regular review during which is installed in the coudé room of obtained in the first NTT observations, construction. the 3.6-metre telescope and is now the thanks to the newly implemented active – Hardware costs were to be paid by only instrument offered at that telescope. optics, was as yet unknown. A number of ESO, while the staffing provided by the As shown in Table 1, data taken with other factors led to the approval of the institutes would be compensated by the instrument have been used for close VLT, including: the preparatory work that observing nights with the instrument to 700 publications since its installa- ESO carried out with technical studies in (called Guaranteed Time Observations tion, making it the most successful planet house; the organisation of meetings [GTO]). hunter in ground-based astronomy. focussing on the science and design

4 The Messenger 171 – March 2018 Instrument name Acronym Type Operation time Team information FOcal Reducer/low dispersion FORS1 Vis. I,S,P 1999–2009 PI I. Appenzeller, Co-PIs R. Kudritzki & K. Fricke (Germany) Spectrograph 1 Infrared Spectrometer And Array Camera ISAAC NIR I,S 1999–2013 PI A. Moorwood (ESO), PM A. van Dijsseldonk, IS J. G. Cuby FOcal Reducer/low dispersion Spectrograph 2 FORS2 Vis. I,S, P 2000 —> See FORS1 UltraViolet-Visual Échelle Spectrograph UVES Vis. Éch. 2000 —> PI S. D’Odorico (ESO), PM H. Dekker, IS A. Kaufer Nasmyth Adaptive Optics System NACO NIR AO I,S 2 0 0 2 —> PIs R. Lenzen (Germany) & G. Rousset (France) (NAOS)-CONICA VIsible Multi-Object Spectrograph VIMOS Vis. MOS 2 0 0 3 —> PI O. LeFèvre (France), Co-PI P. Vettolani (Italy) Fibre Large Array Multi Element Spectrograph FLAMES Vis. MFS 2 0 0 3 —> PI L. Pasquini (ESO), Co-PIs A. Blecha (Switzerland), C. Cacciari (Italy), M. Colless (Australia), F. Hammer (France) Spectrograph for INtegral Field Observations SINFONI AO NIR IFS 2 0 0 4 —> PIs N. Thatte & F. Eisenhauer (Germany), in the Near Infrared Co-PI T. de Zeeuw (Netherlands), H. Bonnet VLT Imager and Spectrometer for mid-InfraRed VISIR MIR I-S 2 0 0 5 —> PI P. O. Lagage (France), Co-PI W. Pel (Netherlands) Cryogenic InfraRed Échelle Spectrometer CRIRES NIR Éch. 2007–2014e —> PI H.-U. Käufl (ESO), PM J. Pirard High Acuity Wide fieldK -band Imager HAWK-I NIR I AO 2 0 0 8 —> PI M. Casali (ESO), PM J. Pirard, IS M. Kissler-Patig X-shooter X-shooter NIR Éch. 2 0 0 9 —> PIs S. D’Odorico (ESO), F. Hammer (France), L. Kaper (Netherlands), P. Kiærgaard (Denmark), R. Pallavicini (Italy), PM H. Dekker, IS J. Vernet K-band Multi-Object Spectrograph KMOS NIR MOS 2 0 1 3 —> PIs R. Sharples (UK), R. Bender (Germany) Multi Unit Spectroscopic Explorer MUSE Vis. IFS AO 2 0 1 4 —> PI R. Bacon (France), Co-PIs T. de Zeeuw (Netherlands), S. Lilly (Switzerland), H. Nicklas (Germany), J. P. Picat (France), M. Roth (Germany) Spectro-Polarimetric High-contrast SPHERE NIR AO I,S,P 2 0 1 5 —> PI J. L. Beuzit (France), Co-PI M. Feldt (Germany) REsearch instrument Échelle SPectrograph for Rocky Exoplanet- ESPRESSO Vis. Éch. 2 0 1 8 —> PI F. Pepe (Switzerland), Co-PIs S. Cristiani (Italy), R. Rebolo-Costa and Stable (Spain), N. Santos (Portugal) Enhanced Resolution Imager and Spectrograph ERIS NIR I,S AO 2020 (tbc) PI R. Davies (Germany), Co-PIs S. Esposito (Italy), M. Kenworthy (­Netherlands), M. Macintosh (UK), S. Quantz (Switzerland) Multi Object Optical and Near-infrared MOONS Vis.–NIR MFS 2021 (tbc) PIs J. Afonso (Portugal), M. Carollo (Switzerland), M. Cirasuolo (ESO), Spectrograph R. Maiolino (UK), H. Flores (France), T. Oliva (Italy), L. Vanzi (Chile),

The resulting instrument collaborations outside ESO and this percentage is even Table 2. VLT Instruments from first light in 1999 to included advantages for both parties. higher for the second generation. The 2018. The second column lists the wavelength bands (Vis. visible, NIR near-infrared, MIR mid-infrared) and For ESO it enabled an ambitious instru- contribution of ESO to the external instru- instrument capabilities, which are described as fol- mentation programme within budget and ments has been significant; all the detec- lows: AO adaptive optics, Éch échelle spectroscopy, on schedule; it gave access to unique tor systems (visible and NIR) were pro- I imager, IFS integral field spectroscopy, MFS multi- expertise that was nurtured in national cured, integrated and optimised by ESO. ple fibre spectroscopy, MOS multi-object spectros- copy, P polarimetry and S spectroscopy. The Team institutes; and it fostered a sense of Other significant examples of ESO deliv- information lists the Principal Investigators (PIs) and ­ownership of the VLT programme in a erables are the AO systems for SINFONI, Co-PIs. The latter were members of the consortium significant fraction of the astronomy com- MUSE and HAWK-I and the large échelle responsible for the project in their institute or for munity. For the institutes it led to the grating unit for ESPRESSO. their country. In the case of ESO-led projects, pro- ject managers (PM) and instrument scientists (IS) are ­creation of competent, multidisciplinary also given. instrument teams around an ambitious Table 2 lists all of the instruments at the project, and made it easier to obtain VLT today as well as the two that have analysis of statistics of ESO observing funding from national agencies to been decommissioned and two that are proposals, and of the number of publica- develop the necessary infrastructure, in an advanced stage of construction. tions and the corresponding citations, including integration and testing facilities. The operational lifetime of the first instru- has been carried out by ­Leibundgut et al. ments has clearly exceeded the original (2017) and concludes, “all VLT instruments Finally, GTO provided the opportunity to estimates of a maximum of ten years of are in constant demand, display a good carry out programmes that could have a operation. This has been made possible scientific return and show significant significant scientific impact. This synergy by the homogeneous and high standards ­scientific impact”. The fact that citation between ESO and the different national that were set for all instrument specifi­ counts continue to increase for all opera- groups has produced a unique set of cations and by effective maintenance tional instruments is an indication of their high-quality instruments and greatly con- procedures at the Observatory. Technical ongoing competitiveness. tributed to the growth of ground-based interventions and upgrades have been astronomy in Europe. Seven out of 11 carried out when needed to keep instru- Interferometry was a key objective of the first-generation instruments were built ment performance competitive. A detailed VLT from its conception. Table 3 lists the

The Messenger 171 – March 2018 5 Telescopes and Instrumentation D’Odorico S., 40+ Years of Instrumentation for the La Silla Paranal Observatory

Table 3. VLTI instru- Instrument name Acronym Instrument type Operation time Team information ments and key infor­ VLTI Commissioning VINCI K, 2-beam 2001–2011 PI V. Coudé du Foresto (France), mation about the Instrument Co-PI P. Kervella (France, ESO) ­instruments and the Astronomical Multi-BEam ­ AMBER H-K, 3-beam, 2 0 0 4 —> PI R. Petrov (France), Co-PIs F. Malbet (France), instrument building combineR SC K.-H. Hofmann (Germany) teams. PIs and Co-PIs are defined as in Table 2. Mid-infrared Interferometric MIDI N, 2-beam, 2003–2015 PI C. Leinert (Germany), Co-PIs G. Perrin The instrument type lists ­instrument SC (France), R. Waters (Netherlands) the wavelength band Precision Integrated-Optics PIONIER H-K, 4-beam, 2 0 1 1 —> PIs J. P. Berger, J. B. Le Bouquin (France) covered, the number of Near-infrared Imaging ExpeRiment I coherently combined telescope beams and GRAVITY Gravity K, 4-beam, 2 0 1 6 —> PI F. Eisenhauer (Germany), Co-PIs K. Perraut the type of instrument I Astr., SC (France), G. Perrin (France), C. Straubmeier using the following (­Germany), W. Brandner ­(Germany), A. Amorim (P) abbreviations: Astr. Multi-AperTure mid-Infrared MATISSE L- N, 4-beam, 2 0 1 9 —> PI B. Lopez (France), Co-PIs T. Henning ­(Germany), ; I 2D imag- ­SpectroScopic Experiment I, SC G. Weigelt (Germany), W. Jaffe (­Netherlands), ing; and SC spectro- F. Vakili (France) scopic capability.

CASPEC 1983 EMMI 1989 ISAAC 2002

UVES 2000 X-shooter 2008 MUSE 2013

Figure 2. This mosaic of ESO instruments spanning Lizon á l’Allemand, the long-time head of the Integra- many other members of the ESO personnel in 30 years of ESO history illustrates that the organisa- tion and Cryogenic Group, at work during the testing Garching and in Chile. It is a useful reminder of the tion is made up of individuals, not just of a sequence and integration of instruments for La Silla and importance of in-house technical expertise and of of projects. In this case the photos show Jean-Louis Paranal. Equivalent pictures could be made up for the dedication of ESO staff to their unique jobs.

6 The Messenger 171 – March 2018 main VLTI instruments. These are located We are now approaching 20 years of Directors General, and to thank A. Glindemann, at the focus for coherent combination of VLT operation. The procedure set up J. L. Lizon and L. Pasquini for supplying their unique knowledge for this article. The publication statistics the light beams from the four dedicated more than 25 years ago for the definition are from the public ESO Telescope Bibliography, 1.8-metre Auxiliary Telescopes (ATs) or and procurement of instruments has maintained by the ESO Library. from the 8-metre telescopes. In practice, been consolidated and proven to be very owing to the special requirements and successful. It has inspired similar References exploratory nature of the interferometric approaches at all other major observa­ observations, all of these instruments tories worldwide. The 39-metre ELT De Zeeuw, T. et al. 2017, The Messenger, 169, 64 have been developed by national institutes ­telescope project that ESO is embarking D’Odorico, S., Moorwood, A. & Beckers, J. 1991, in close collaboration with the VLTI group on now opens up a new scenario. The Journal of Optics, 22, 85 Leibundgut, B. et al. 2017, The Messenger, 169, 11 at ESO. Coherent combination of the light unique properties of the AO-based tele- Madsen, C. 2012, The Jewel on the Mountaintop, from the 8-metre Unit Telescopes has scope — the largest photon collecting (Weinheim: Wiley-VCH) been carried out for more than a decade area ever in one telescope — and the Patat, F. et al. 2017, The Messenger, 169, 5 now, but ESPRESSO, a high stability need to optimise the use of precious Woltjer, L. 2006, Europe’s Quest for the Universe, (EDP Sciences) échelle spectrograph that is being com- observing time require new thinking in the missioned at the Paranal Observatory, selection and design of instrumentation is the first instrument which can be fed as well as in its operating mode(s). These Links by the incoherent beam/(s) from either a are the exciting challenges that the ESO 1 Convention and Protocols, European Southern single telescope or multiple telescopes. community faces over the next decade. Observatory (January 1987): https://www.eso.org/ It will open up new parameter space in public/archives/books/pdf/book_0017.pdf both limiting magnitude and wavelength accuracy, in high resolution spectroscopy Acknowledgements Notes at ESO. The instrumentation effort at ESO has involved the contributions of more than a hundred members a EFOSC2 was at the 2.2-metre telescope from 1991 In the last decade the cooperation of ESO staff over the last 40 years. This includes to 1997, at the 3.6-metre telescope from 1998 to between ESO and its community on designers, managers, engineers, technicians, physi- 2007 and at the NTT from 2008. b The following La Silla instruments were built by Paranal has not been confined to the cists and astronomers, both at ESO Headquarters and at the Observatory in Chile. Their role has often consortia in collaboration with ESO. Some more VLT but has led to the installation of two been decisive in determining the success of the pro- information about their teams is listed below: additional powerful telescopes. The jects. It is impossible to acknowledge their contribu- – TIMMI2: PI H. G. Reimann (Germany), Co-PIs VISTA 4-metre survey telescope with an tion individually here. H.-U. Käufl (ESO) and H. Hron (Austria). – HARPS: PI M. Mayor (Switzerland), Co-PIs infrared camera (VIRCAM), covering a It is equally impossible to give the corresponding list W. Benz (Switzerland), J. P. Sivan (France) and field of 1.65 degrees in diameter, was of people from the institutes in the ESO member L. Pasquini (ESO). delivered by the UK in 2007 as an in-kind states who provided unique expertise and supplied – WFI: PI K. Meisenheimer (Germany), Co-PIs payment when it joined ESO. The 2.5- fully working instruments. The names of external PIs M. Capaccioli (Italy) and D. Baade (ESO). – FEROS: PI B. Wolf (Germany), Co-PIs metre VLT Survey Telescope (VST) was and Co-PIs of the instruments in Tables 1, 2 and 3 are just a reminder of the massive external contribu- J. Andersen­ (Denmark), A. Kaufer (Germany) installed by the Italian­ National Institute tion to instrumentation. The full list of those involved and L. Pasquini (ESO). for Astrophysics in 2011 and is equipped with their responsibility in the different projects c FEROS was at the 1.52-metre telescope between with a 1 × 1 degree field CCD camera can be found in the publications quoted in the ESO 1999 and 2002. instrument pages. d The 2.2-metre telescope was installed on long-term (OmegaCAM), which was developed by loan from the Max-Planck-Gesellschaft and has not a consortium from the Netherlands, Finally, I would like to mention the key role of been offered for time at ESO since 2014. ­Germany, Italy and ESO. A. Moorwood, with whom I shared 30 years of e CRIRES has not been offered to the community ESO instrumentation activities, working under five between 2014 and 2018 because of an upgrade project. )/ESO atacamaphoto.com G. Hüdepohl (

The VLT/I at sunset.

The Messenger 171 – March 2018 7 Telescopes and Instrumentation DOI: 10.18727/0722-6691/5062

End-to-End Operations in the ELT Era

Olivier R. Hainaut1 (DFS; Quinn 1996). It was designed Evaluation of the end-to-end process Thomas Bierwirth1 between 1994 and 1995, and deployed Stéphane Brillant1 on the NTT between 1996 and 1997 dur- In addition to being the backbone of the Steffen Mieske1 ing the “NTT Big Bang”, when that tele- operations of about 20 instruments on Ferdinando Patat1 scope was overhauled to become a pro- 12 telescopes over two sites, the DFS Marina Rejkuba1 totype of the new VLT standard. provides a rather homogenous interface Martino Romaniello1 for users (including both the community Michael Sterzik1 The main building blocks of the DFS were and internal users). The system must be already implemented at that time as a sufficiently versatile and flexible to cope series of interconnected but standalone with this complexity and to incorporate 1 ESO processes and tools: proposal handling; new and continuously evolving instru- observation handling; maintaining the ments. In particular, the DFS will have to ­science archive; and data processing efficiently support ELT operations. Fur- The Data Flow System is the infrastruc- pipelines. One of the key concepts at the thermore, sub-processes and the corre- ture on which Very Large Telescope core of the original DFS was the Obser- sponding tools must pass information (VLT) observations are performed at the vation Block (OB), the quantum unit that from one stage to the next one effec- Observatory, before and after the obser- defines all the information required to tively, avoiding duplication and averting vations themselves take place. Since execute an independent set of observa- inconsistencies. its original conception in the late 1990s, tions on a specific target. Over time, the it has evolved to accommodate new system has become more complex as Besides these top-level requirements, observing modes and new instruments new types of observing programmes the evaluation of the DFS incorporates on La Silla and Paranal. Several updates have been added, including new modes the ELT top-level requirements, and the and upgrades are needed to overcome and new concepts on top of the individ- requirements derived from the future its obsolescence and to integrate ual OBs (for example, containers in the instruments (in particular from the Echelle requirements from the new instruments ESO Public Surveys). Many tools under- SPectrograph for Rocky Exoplanet and from the community and, of course, from went substantial changes and upgrades Stable Spectroscopic Observations ESO’s Extremely Large Telescope (ELT), to cope with these new concepts and [ESPRESSO], the 4-metre Multi-Object which will be integrated into Paranal’s technical requirements, while others grew Spectroscopic Telescope [4MOST] and operations. We describe the end-to-end more organically. the Multi Object Optical and Near-infrared operations and the resulting roadmap Spectrograph [MOONS]). It also includes guiding their further development. The DFS gradually evolved to reach the the results of a review of the current sys- current implementation (Figure 1). The tem, summarised in a series of Messen- core concepts of the system are robust ger articles (Primas et al., 2014 for SM; The origins (for example, the quantum unit of the Romaniello et al., 2015 for the Archive, OB to define observations) and a set of Arnaboldi et al., 2014 for Phase 3; Sterzik At the time of the construction of the VLT interfaces ties the tools together. Never- et al., 2015 and Patat et al., 2017 for sci- in the late 1990s, it was already becoming theless, in many areas the tools have entific return). The feedback from the clear that the “classical observing cycle grown beyond a level at which they can community has been assimilated through of trekking to the telescope and returning be efficiently maintained, are based on the ESO2020 workshop and poll (Primas home with a tape of unprocessed data”, aging technologies, and/or don’t take et al., 2015) and the recommendations of as Quinn (1996) described it, was no advantage of new technical capabilities. the ESO2020 Time Allocation and Sci- longer the most efficient way to deal with Furthermore, the original concept of data ence Data Management working groups, the coming generation of 8- to 10-metre flow has been broadened to include not as well as input from ESO’s advisory telescopes. The first paradigm change only the data themselves, but also the bodies: the Scientific Technical Commit- introduced by ESO was Service Mode whole operation process, from the origi- tee and the Users Committee. (SM), in which pre-defined observations nal proposal for observing time to the are executed when the observing condi- distribution of science-ready data pack- The tools and facilities offered in other tions match those needed for the specific ages — i.e., an “end-to-end operations” observatories were also examined to esti- science case. The second was to guar- process. Last, but not least, ESO is build- mate the evolving astronomical environ- antee the calibration of the instruments to ing the ELT, and one of its top-level ment and the possibility for their re-use in a pre-defined level of accuracy and to requirements is that its operations must ESO’s tools. Finally, the need to ensure allow archive science, implying a well-­ be fully integrated with Paranal. that the DFS could be maintained over an defined calibration plan and continuous expected lifetime on the order of 20 years quality control of the calibration process. The time has come for an in-depth guided any technological choices. Quinn also noted that a direct conse- review of ESO’s Data Flow System, and quence of this was that the “flow of data a (r)evolution. All the new requirements were assessed; must be managed from start to end of while some are indeed novel, they are all the observation process”, resulting in the compatible with the current fundamental development of the Data Flow System concepts — even if not with the current

8 The Messenger 171 – March 2018 Figure 1. End-to-end Observatory operation process: the Long-term scheduleSObservation ervice Mode queues main sub-processes are indicated in boxes; the preparation Obse background colour indi- rv at cates the main actors io Scheduling n blocks involved in each step. The arrows are labelled Phase 2 with the information flow- Observation blocks Short-term Programme ing over them. This “DFS schedule Wheel” is an adaptation selection of the original one pre- sented by Quinn (1996). Observing programmes While the overall process will not change much Programme Visitor Mode Observation over the deployment of preparation User community the upgrades described execution s Phase 1 in this roadmap, many of the sub-processes statu

Observation proposals edback

y and the tools implement- fe ing them will undergo in- plan qualit depth, and often com- Science n plete, re-implementation. pr Raw data Phase 3 oces Science-grade data products Advanced data products data usag s Sc w Calibratio Data papersienc Ra Instrument e statistics e Science Archive Quality control Raw + processed data Publication + curation Raw data Data reduction + preservation

Master calibration frames ESO HQ Science-grade data products tools — implying that the overall end-to- of this exercise, so they were already user- or science case-specific scripts and end operations, which has been in use ­collecting requirements and evaluating even desktop applications can be built since the start of VLT operations, is still costs. Others will take place in several against these APIs. The strict separation sound. What is needed is an in-depth years’ time; these have been estimated of user interface and business logic has “clean-up” and update of the system from the complexity of the existing enormous advantages in terms of main- rather than a complete re-engineering. As ­system and the additional requirements. tainability. Rather than asking users to no exotic or extreme new requirement The preliminary estimates will be refined download and install new software ver- was identified, we did not investigate when the projects actually start — in the sions ESO can seamlessly fix bugs and ­different operation schemes in detail. The meantime they are sufficient for planning roll out new features by deploying new new end-to-end operations model will the roadmap presented here. software to an ESO server for immediate be a modernisation of the current one, availability to all users. building on the many years of experience In the following section, we offer an operating the VLT and, before that, ­overview of these projects and, by way The paradigm chosen is the representa- La Silla. of illustration, delve into some of them in tional state transfer (REST), an industry more detail. standard that the contracted software All sub-processes were assessed, and engineers are familiar with. Additionally, areas requiring work were identified. there are now powerful web frameworks An overall high-level plan was designed Roadmap towards a new data flow that enable fast development of powerful, and broken down into individual projects. system large-scale user interfaces. The frame- The dependencies between these pro- work chosen is Google’s Angular 5. User jects were accounted for, together with Platform interfaces tend to age faster than the specific milestones (for example, the first underlying business logic. Thanks to their light of a given instrument) as well as the Breaking with a long tradition of requiring separation, interfaces can be updated savings that they will generate in terms users to install and deploy programs on without requiring a re-implementation of of maintenance and operations. The their own computers, new tools are being the business logic. Also, as the APIs are resources in time, equipment and staffing developed using application program- exposed (and documented), power users were evaluated for each project. Some of ming interfaces (APIs) to services hosted can access them directly using scripts to these projects were ongoing at the time at ESO. Web-based user interfaces and execute series of commands that would

The Messenger 171 – March 2018 9 Telescopes and Instrumentation Hainaut O. R. et al., End-to-End Operations in the ELT Era

be cumbersome from a web interface; Observing Tool (vOT version 4) have been Currently, the first two modules — which indeed, users can even develop their own deployed for Visitor Mode support during define what is offered in an observing custom interfaces. 2017. The deployment for Service Mode cycle and how to define and submit pro- will be done in two phases in 2018, first posals — are under development and are Before the observations on Unit Telescope 2 (UT2) and on the expected to be delivered in the first half of survey telescopes for Period 101, followed 2018. The next modules (OPC administra- Phase 1 includes the release of details by implementation on all Paranal tele- tion, handling OPC rankings, interactions of what is being offered in a particular scopes for Service Mode for P102. A with the submitters) will be developed in observing cycle through a Call for Pro- second wave of developments that will 2018 and 2019. The overall integration posals, the preparation of proposals for include specific VLTI and Adaptive Optics will take place in 2020 and we expect to observing time by the community, the operational requirements, enable defini- have the new system in place by the end handling of these proposals, and the tion of complex observing strategies of 2020. While it would be nice to deploy organisation of and support to the through nested scheduling containers, the new proposal submission system Observing Programme Committee (OPC), and also enable more streamlined con- earlier, its deeply rooted interconnections which reviews the observing proposals nections with the Phase 1 ETCs will take with the rest of the Phase 1 infrastructure submitted. The Principal Investigators (PIs) place in 2019. The inclusion of the La Silla make that impossible. From the user point and co-investigators (Co-Is) of successful operations in the new P2 system will take of view, the proposal submission will be proposals then prepare the detailed spec- place in 2018-2019, in time for the new fully web-based, supporting collaborative ifications of their observations — the OBs instruments NIRPS and SOX. Once this is work from the PI and Co-Is. Figure 2 — during Phase 2. Both Phase 1 and done, we will be able to decommission shows screenshots of the P1 and P2 web Phase 2 activities are supported by expo- the legacy P2PP and underlying servers. user interfaces. sure time calculators (ETCs). Phase 1 Exposure time calculators (ETCs) Following the plan, all tools related to The Phase 1 support tools include the The ETCs are already web-based, but Phase 1 and 2 and the ETCs will be mod- long-lived ESOFORM, a LaTeX package implemented in a way that precludes ernised through the implementation of that has been used to define proposals easy interaction via scripts (or from other REST APIs and web interfaces. These for observing time since Period 60 (we tools like Phase 1 and Phase 2 prepara- projects have started and are at different are now in Period 100). However, the tion) and that uses specific models for stages of implementation. ESOFORM is only the tip of the iceberg of the instruments. This makes their main­ Phase 1 tools. A series of tools process tenance cumbersome and their integra- Phase 2 the LaTeX files of the observing proposals tion and use in batch mode difficult. For operational reasons, the Phase 2 and store some of the information in a The ETC upgrade project was initiated in ­systems were the first to be upgraded. database (unfortunately the LaTeX format 2017 and will likely be completed by They had already been updated to sup- means that some important information 2020. Some features of the user inter- port survey operations on the Visible and cannot be stored in such a way that can faces at other observatories, such as the Infrared Survey Telescope for Astronomy be easily retrieved programmatically), possibility to save and share ETC ses- (VISTA) and the VLT Survey Telescope deal with the administration of the OPC sions, are included in the requirements. (VST) in 2010 and 2011, with the addition and the OPC reviewer rankings and Thanks to the modular structure of the of scheduling containers. However, it was ­recommendations, interface with the ETCs, the benefits of the new system will already recognised in 2014 that the cur- scheduling system, and finally handle the appear gradually on the ETC web pages. rent system would not be able to respond communication to the proposers. to the requirements from ESPRESSO’s The new P1, P2 and ETC systems share planet-hunting strategy and massive The maintenance of these tools has exactly the same authoritative instru- spectroscopic surveys with 4MOST. The become cumbersome, and integrating ment definition model as that used for Java desktop application called P2PP new requirements (for example, the the instrument itself (i.e., the Instrument (Phase 2 Proposal Preparation) was ­recommendations from the ESO2020 Packages), ensuring consistency introduced in 1997, replacing the original Time Allocation working group) would be between the tools. The tools will also be Tcl/Tk application. It is now being impractical. These tools and the under­ able to interact and exchange information replaced by the new API-based P21, lying databases have grown organically. using their APIs. This will make a tight which reproduces its functionalities while In terms of technology and architecture, integration possible between the ETCs adding new ones. With P2, the user they require a complete redesign and and the P1 and P2 systems; all the cal­ ­creates OBs and stores them directly on implementation. Because of the tight culations performed to estimate the tele- the Garching repository. A bi-directional integration of all of the Phase 1-related scope time required for a Phase 1 pro- database replication­ ensures that the subsystems, and because of the funda- posal are preserved in the proposal itself, OB’s content is the same in both the mental changes in the underlying infra- and will be available as the basis on which Garching and the Paranal repositories. structure, the change from the old to the to optimise the observing strategies at new system can only take place when the Phase 2. The ETC API will also make sim- The P2 project was started in 2016; the whole system is ready. ulations available for Quality Control P2 web tool and the matching visitor ­processes (see the After the observations

10 The Messenger 171 – March 2018 Figure 2. Screenshot of the P1 and P2 web tools developed to prepare proposals and observations.

tools are too complex for implementation in current web technologies, we devel- oped a platform and implemented it as a plug-in to the Aladin sky atlas tool2. This becomes the basis for all future obser­ vation preparation tools. This new tool, GuideCam3, is already available for various instruments (Figure 3). Existing prepara- tion tools for other instruments that will not be decommissioned in the foreseea- ble future will be retrofitted to GuideCam over the coming years. In 2018, Guide- Cam will also include a generic system to produce finding charts, to replace the aged SkyCat tool; this will make it much simpler to prepare Service-Mode-compli- ant finding charts. Furthermore, thanks to the integration between GuideCam and the P2 system, information will be section), and to investigators who want configuration (for example, fibre positions embedded in finding charts and will be to explore a broad range of parameters on a multi-object spectrograph). These available to the staff reviewing and exe- or apply a simulation to a catalogue of are currently defined using a suite of cuting the observations. objects. ­auxiliary preparation tools (for example, FORS Instrument Mask Simulator [FIMS], Towards a unified GuideCam tool KMOS ARM Allocator [KARMA]), many of OBs for several instruments must include which are based on the increasingly very specific details on the instrument ­outdated Tcl/Tk technology. As these Figure 3. Screenshot of the Unified GuideCam Tool.

The Messenger 171 – March 2018 11 Telescopes and Instrumentation Hainaut O. R. et al., End-to-End Operations in the ELT Era

Scheduling the observations and user-specified priorities, as well as After the observations Long-term telescope schedules are for the prevailing conditions. ORANG assembled by accounting for a number of also takes into account additional con- Science Archive factors, including the ranking of Phase 1 straints such as time criticality and links The Science Archive System has always proposals by the OPC, ESO high-level between OBs in OB containers. However, been considered the final repository of science operation policies4 and any con- ORANG has no capabilities to account VLT data, thus preserving their legacy straints specified in the proposals them- for the evolution of the observing condi- value. Over time, its role has become selves — both deterministic (for example, tions. We are working with the Paranal more and more central in overall opera- target coordinates and the phase of the astro-weather group to integrate informa- tions. Thanks to advances in the internet, Moon) and statistical (such as image tion provided by the Astronomical Site its role now also includes the distribution quality). The output of the new P1 system Monitor that goes beyond established of data to both the original PI as well as will enable a much finer granular account- weather parameters such as cloud trans- to other independent archive research- ing of the constraints and geometry than parency and seeing, including water ers. Teams leading Public Surveys and the current system, ensuring that all of vapour pressure, turbulence profile, etc. Large Programmes deliver large, consist- the information relevant for scheduling ent, science-ready datasets called the and observations execution is fully Furthermore, ESO has embarked on External Data Products to the Archive via captured. ­several investigations with weather fore- the Phase 3 process (Arnaboldi et al., casting institutions (both academic and 2014). In parallel, the development of sci- The scheduling tool that is currently commercial) to refine the existing forecast ence-grade pipelines has enabled ESO deployed treats VLT units separately to suit astronomical needs. The goal is to to systematically process the data from a and the only case requiring coordinated be able to forecast the main parameters (growing) number of instruments, creating allocations on multiple Unit Telescopes that are relevant to the observations — the Internal Data Products (Romaniello (i.e., the VLTI) has been managed manu- and, even more importantly, how they et al., 2016). Both raw data and science- ally, within pre-allocated slots. The start change — with a precision that can assist grade data products are very popular of ESPRESSO operations, with its capa- in the selection of future OBs. We will likely with the community, with the number of bility of operating in Service Mode at review and upgrade the STS to account users and the request rate steadily any UT during the night, poses a new for astro-weather forecasts, with the ulti- increasing (Romaniello et al., 2016). challenge, which can only be addressed mate goal of forecasting the seeing condi- by a parallel approach to VLT scheduling. tions and the turbulence profile, as these However, the core archive services — the This requires a radical change to the are particularly critical for the operation of ensemble of web interfaces and underly- scheduling paradigm. the AO-assisted instruments — especially ing system — have not evolved much on the ELT. In parallel with this functional since their deployment in the late 1990s, Therefore, we also plan to update the upgrade, a complete re-implementation while web and database technologies current Telescope allocation Tool (TaToo). of the underlying Observation Tool (OT) is have flourished and the Virtual Observa- The new scheduling tool will enable required by its outdated code base. While tory (VO) protocols have matured. A pro- ­complex strategies, such as simultane- the preliminary studies are already ongo- ject to re-implement the Archive Services ous or sequential scheduling on multiple ing, the project itself will be launched only is underway. Its goal is to let the users telescopes, therefore addressing opera- in 2020; we hope to have the astro- search for and discover ESO data, taking tional requirements for ESPRESSO. This weather forecast module in place in 2022, advantage of the detailed and consistent project is expected to start in early 2019, and the full OT/STS deployed in 2023. metadata describing them, either through once the later phases of the P1 project an interactive web interface, or through are underway. In addition to these visible changes, a a VO-compliant API for more complex series of behind-the-scenes projects queries. The API will also open the archive Observations need to take place. For instance, the Data to the available VO tools (for example, Handling System (which moves data Aladin, TopCat, etc). Finally, the Archive Observations on the mountain are either between workstations at the Observatory will offer previews of its assets, allowing performed in Visitor Mode, for which the before bringing them to the Science users to quickly evaluate the suitability observer travels to La Silla or Paranal to Archive) has been maintained since its of a file for their purposes. The previews execute and fine-tune their observations creation, but has never been re-evaluated include progressive multi-scale images in real time, or in Service Mode. For a at the overall process level. The integra- (c.f. Google Earth), which will be broad- Service Mode run, the observer selects tion of the requirements from the ELT, as cast via the HiPS network 5. Thanks to the observation to be performed from well as from the Quality Control project this, services like ESASky 6, which gives the pool of Phase 2 OBs, executes it and (see below) is a good opportunity. This access to a highly curated subset of evaluates its success based on fulfilment will take place in parallel with the imple- ­multi-wavelength/multi-observatory data, of predefined observing parameters. The mentation of the interfaces to the ELT will also be able to access, display and selection of the “best” OB for execution between 2021 and 2023, including both retrieve suitable ESO data – for instance, is assisted by the Short-Term Scheduler “front end” (from the DFS to the ELT con- data products from large surveys. The first (STS), also called the OB Ranking Engine trol system) and “back end” (from the ELT release of this new Archive Service, which (ORANG), which accounts for policies back to the DFS). will include most of the data products, is

12 The Messenger 171 – March 2018 scheduled around the time of publication Data processing and pipelines Conclusions of the present article and will be described infrastructure in detail in the next issue of the Messenger. The QC system, the online pipelines (at An ambitious roadmap has been devel- Paranal) and offline pipelines (on users’ oped to overhaul the dataflow system Quality control (QC) machines) rely on a series of data organi- supporting the VLT observations, the ulti- One of the key concepts of the original sation tools (for example, to select and mate aim being to accommodate the DFS was the introduction of a formal associate suitable calibration files) and requirements of ELT and new VLT instru- ­calibration plan ensuring that instruments data processing infrastructure that calls ments, and to ensure the system’s future can be calibrated to a pre-defined accu- and manages pipeline recipes (for maintain­ability. This plan has been devel- racy; the operations plan ensures that all instance, ESOrex, and the workflow sys- oped and endorsed internally at ESO. An the required ancillary frames are acquired tem Reflex). The pipeline recipes them- external review is taking place to ensure and the quality control (QC) system veri- selves are implemented using the low- its completeness, review its soundness fies their validity and suitability through level Common Pipeline Library, and more and evaluate synergies with similar devel- instrument health and trending parame- advanced algorithms from the High-level opments at other observatories. The ters. A QC infrastructure has been devel- Data Reduction Library. The suitability developments are being staged to max- oped over the years to monitor the instru- of these tools will be reviewed in the imise the use of finite resources, while ments and detect deviations from their coming years accounting for new internal meeting deadlines. One of the main goals specifications before the instrument per- and community requirements (for exam- is to integrate all of the sub-processes formance significantly degrades. The QC ple, interfacing with Python) and new and make the overall end-to-end opera- also produces certified calibration frames, capabilities (for example, cloud comput- tions seamless, both for the users and for which are stored in the Archive and can ing). The outcome of this review will lead the operators. While many new tools and be used by the pipelines for the science to an evolution of pipeline systems and systems will be deployed as soon as they data processing. their infrastructure. Whilst the scope and become available, some require major nature of this project are not defined yet, infrastructure changes and must there- This infrastructure is robust and flexible, resources have been earmarked between fore be completed before they can enter but uses a technology that has issues 2020 and 2021. operations. The ultimate deadline for this in terms of maintainability. Furthermore, series of projects is ELT first light. we are now in a situation where the scope of QC can be expanded beyond the cali- Infrastructure bration and instrument stability. A QC References infrastructure can be deployed directly at The DFS relies on a series of infrastruc- Arnaboldi, M. et al. 2014, The Messenger, 156, 24 the telescope, together with the online tures, which must be maintained and de Zeeuw, T. 2016, The Messenger, 166, 2 pipelines, to provide a systematic real- allowed to evolve. A couple of examples Patat, F. et al. 2017, The Messenger, 170, 51 time assessment of many parameters of are given below. Primas, F. et al. 2014, The Messenger, 158, 8 the data as it is acquired. This will help Primas, F. et al. 2015, The Messenger, 161, 6 Quinn, P. 1996, The Messenger, 84, 30 to evaluate observations from new com- The first is the Next Generation Archive Romaniello, M. et al. 2016, The Messenger, 163, 5 plex instruments, for which raw data System (NGAS), the storage technology Sterzik, M. et al. 2015, The Messenger, 162, 2 are so entangled that an inspection of developed for the Science Archive. raw frames would not be sufficient to NGAS has evolved over the past decade, Links judge their quality (for example, integral and is now, either directly or indirectly, field units and interferometric instru- used at ESO, ALMA and other institutions. 1 Phase 2 demo environment: https://www.eso.org/ ments). Furthermore, the pipeline genera- As storage technologies evolve rapidly, p2demo 2 tion of science-grade processed data NGAS must also follow. Aladin sky atlas: aladin.u-strasbg.fr 3 The unified GUideCam Tool:www.eso.org/sci/ implies that the data quality is also evalu- observing/phase2/SMGuidelines/GUCT.generic. ated in a systematic way. Finally, the The DFS also depends on many data- html ­traditional instrument calibration QC pro- bases; while our demands are fairly 4 VLT/VLTI Science Operations Policy: eso.org/sci/ duces parameters that can be compared ­modest by modern standards, we have observing/policies/Cou996-rev.pdf 5 Hierarchical Progressive Surveys (HiPS): directly with the output of the instrument original requirements (such as our mul- ­aladin.u-strasbg.fr/hips simulators, closing the loop between the ti-site architecture, or the spherical 6 ESASky: sky.esa.int ETCs and the actual instrument. Thanks geometry of the celestial sphere), which to the ETC API, deviations between are not fully supported by out-of-the-box the simulation and the measurement can products. Furthermore, the landscape result in flagging a problem, or in up­dat- of available database systems is evolving ing the ETC parameters. This major in terms of capabilities, support and cost. ­evolution of the QC processes consti- tutes a significant effort and the project is due to start in mid-2018, with new QC systems deployed gradually until 2022.

The Messenger 171 – March 2018 13 Telescopes and Instrumentation DOI: 10.18727/0722-6691/5063

The VLTI Roadmap

Antoine Mérand 1 ments of the near and mid-infrared emis- consolidation phase. The next challenge sion of bright sources and spectroscopy is to combine increased sensitivity and with milli-arcsecond angular resolution. precision. The next step is phasing (also 1 ESO These reconstructed images have chal- called fringe tracking) of the array of tele- lenged a number of established theories scopes on-axis and, at a later stage, off- in the field of stellar physics and active axis. This will considerably improve the ESO’s Very Large Telescope Interferom- galactic nuclei (AGN). With these images, accessible sizes of the samples and will eter (VLTI) was a unique facility when it the VLTI can now reveal the true under­ enable high-resolution spectroscopy. As was conceived more than 30 years ago, lying complexity of these objects. previous experience — using the Astro- and it remains competitive today in the nomical Multi-BEam combineR with the field of milli-arcsecond angular resolu- The VLTI offers the possibility of spatially Fringe-tracking Instrument of NIce and tion astronomy. Over the past decade, and spectroscopically resolving a range TOrino (AMBER+FINITO) and the MID- while the VLTI matured into an opera- of time-variable astrophysical processes infrared Interferometric instrument with tionally efficient facility, it became lim- that cannot be accessed via other tech- the Fringe Sensor Unit (MIDI+FSU) — ited by its first-generation instruments. niques. It is a tool to challenge our indi- suggests, efficient phasing requires the As the second generation of VLTI instru- rect understanding of stars, explore rota- implementation of a number of subsys- mentation achieves first light, further tion, pulsation, convection, shocks, winds, tems or upgrades, as well as a particular developments for this unique facility are accretion, and ejection phenomena as attention to global performance, including being planned and are described here. they happen and reveal the complex particularly good wavefront correction in interplay between a star and its environ- the UT and AT arrays. ESO has developed ment throughout its lifetime. The capabil- sufficient expertise to tackle this crucial Introduction ity of the VLTI to resolve the complexity step for MATISSE, which cannot deliver of AGN, to precisely measure the central its full potential without phasing. The The VLTI will remain — even in the era black hole mass and to pinpoint its dis- dedicated project called GRAVITY for of ESO’s Extremely Large Telescope tance with unmatched accuracy has not MATISSE (GRA4MAT) is using GRAVITY’s (ELT) and the Atacama Large Millimeter/ yet been exploited. With GRAVITY, the own fringe tracker to phase MATISSE, and submillimeter Array (ALMA) — the Euro- VLTI has become an astrometric machine, is expected to come to fruition in 2019. pean facility with the highest angular offering a unique way to observe strong ­resolution. The past decade has seen gravity in action and explore physical The second challenge is to bring ESO master the difficulties of coherent conditions close to the horizon of the ­GRAVITY up to its ultimate astrometric combination of an optical array with four black hole at the Galactic Centre. As such, performance. This remarkable scientific Unit Telescopes (UTs) or Auxiliary Tele- it offers a rare opportunity for ground- outcome will be delivered thanks to a scopes (ATs). These successes paved the based astronomy to probe the nature of ­significant technological and system effort. way for the ambitious second-generation gravity and contribute to the field of Early results indicate that the short-term instruments: GRAVITY (GRAVITY Col­ ­fundamental physics. The technology astrometric precision is of the order of laboration, 2017a,b) and the Multi AperTure required to enable such an ambitious 50 micro-arcseconds (GRAVITY Collabo- mid-Infrared SpectroScopic Experiment goal will most probably open the way ration, 2017a,b), but the final accuracy (MATISSE) (see Matter et al., 2016; Lopez for more science projects exploiting long-term (over a timescale of months) et al., 2014). Additionally, the VLTI facility micro-arcsecond astrometric capability still needs to be assessed. itself has been upgraded to accommodate from the ground. The powerful combina- the new instruments, bringing improve- tion of fascinating science cases and The third challenge is to democratise ments in both operation and ­performance instrumental innovation is a strong incen- access to the VLTI by providing user (Woillez et al., 2016; Gonté et al., 2016). tive to support the further development of assistance to help with observation prepa- the VLTI. ration, data reduction and image recon- With the VLTI and ALMA, ESO users have struction. The VLTI community has made now gained access to milli-arcsecond The evolution of VLTI infrastructure and considerable progress in this direction, astronomy from the near infrared to the the associated increase in performance for example, through the development of millimetre regimes. Since its inception, should bring trust in our ability to con- reliable software and by running dedicated the VLTI has pursued two goals: deliver- tinue developing milli-arcsecond astron- training schools. However, as revealed ing an imaging capability at the milli- omy from the ground. Whether it will be through polling of the ESO Users Com- arcsecond resolution level and providing by expanding the VLTI or by developing mittee, handling VLTI data is still per- precise relative astrometry with a goal other facilities has yet to be established. ceived as an expert-only activity. ESO is of ten micro-arcseconds precision, addressing this by streamlining the pro- the latter being a much bigger technical cess of preparing VLTI programmes, with challenge. Challenges the goal of shielding users from the com- plexity inherent in earlier VLTI operations, The scientific production of the VLTI has ESO has surmounted the difficulties when combiners used only two or three been vastly dominated by relatively simple associated with optical coherent combi- telescopes and telescope configurations but important morphological measure- nation and the VLTI is now entering a were restrictive.

14 The Messenger 171 – March 2018 The VLTI benefits from a particularly Figure 1. Three-com­ active and dedicated community. Both ponent model of the 100 N dusty environment in the ESO and the VLTI community should ­Circinus galaxy­ based explore a comprehensive interface that on MIDI observations provides users with easier access to (Tristram et al., 2014). data reduction and image reconstruction. E Red, green and blue correspond to wave- 50 Without a doubt, expanding the user lengths of 13 µm, 10.5 ) community will bring new ideas for the µm and 8.0 µm, respec- as tively. Despite their low

scientific exploitation of the VLTI. Between (m surface brightness,

2004 and 2017, nearly 350 individual ion polar outflows account Principal Investigators (PIs) applied for 0 for 80 % of the mid-in- VLTI time. As with any facility, the broad- frared flux in this syn- thetic image. The water ening of the user base also comes when δ Declin at maser disc is deduced new capabilities are offered; the first et fs from centimetre Very few semesters over which GRAVITY has Of Long Baseline Interfero- been offered have brought almost 25 PIs −50 metric (VLBI) observa- who had never used the VLTI before. tions. Reproduced with permission of K. Tristram.

Key scientific questions for VLTI second- −100 1 pc generation instruments

During the next decade, the second gen- 100 50 0 −50 −100 Offset δ Right ascension (mas) eration of VLTI instruments — GRAVITY, MATISSE, and to a certain extent, the using the fringe tracker. The gas in the Binarity across the Hertzsprung Russell ­Precision Integrated Optics Near-infrared inner regions of AGN produces a so-called diagram Imaging ExpeRiment (PIONIER) — are broad line region that can be imaged Increasingly, multiplicity is believed to expected to contribute to many astro- directly by GRAVITY. So far, the only way play a fundamental role in physical domains. We explore a few of to study the broad line region has been and stellar dynamics. An example of the the important ones here. to use reverberation mapping, which fundamental contribution of the VLTI is requires months of photometric monitor- the definitive evidence that massive main The inner of Active Galactic ing. The VLTI can directly resolve the size sequence stars are all in multiple systems Nuclei of the broad line region, and early obser- (Sana et al., 2014). The contribution to GRAVITY and MATISSE are both vations with GRAVITY as well as pioneer- high angular resolution imaging is not lim- expected to contribute to the study of ing work on AMBER indicate that broad ited to binary statistics and also probes AGN. Historically, VLTI observations of line regions are more likely to be compact massive star binaries (Figure 2). Other AGN have been limited to a handful in the than originally estimated by reverberation classes of stars are yet to be studied to K-band by VINCI (Wittkowski et al., 2004) mapping studies (GRAVITY Collaboration, determine their multiplicity fractions; the or AMBER (Weigelt et al., 2012). MIDI has 2017; Pribulla et al., 2011). VLTI could be used to conduct surveys observed several AGN in the N-band but of statistically complete samples of stars the results are puzzling because they Strong gravity in the Galactic Centre with different spectral types. imply that most of the mid-infrared emis- The VLTI instrument GRAVITY has been sion comes from the polar regions, not designed to observe the Galactic Centre. The VLTI is also frequently used to con- the dusty torus as expected (Hönig, 2016). The unprecedented angular resolution duct in-depth studies over a range of Since MIDI was limited to a single base- of the VLTI will help to address several binary systems, for example, the deter­ line, effective imaging of AGN was not questions. The first goal is to measure the mination of independent distances and possible. effects of General Relativity as the star masses at the 1 % level using double- S2 undergoes peribothron in 2018 — i.e., lined eclipsing binaries (Pribulla et al., MATISSE will provide snapshot imaging the point in its elliptical orbit at which it 2011) and resolving wind-wind interactions of AGN, allowing a much more detailed is closest to the supermassive black hole in Luminous Blue Variables (Weigelt et al., view of the morphology of the dust in the Sgr A*. Another goal is to understand 2016). GRAVITY, with its sensitivity and central parsec of galaxies hosting AGN, the origin of the Sgr A* flares which occur spectral coverage (encompassing the full thereby possibly ruling out the simple daily. GRAVITY will help to discriminate K-band, a significant increase on the dusty torus model, as MIDI observations between different scenarios, for example, K-band coverage with AMBER) offers the seemed to imply (Tristram et al., 2014; disc accretion events, accretion of stars, unique capability of spectrally disentan- see Figure 1). GRAVITY is also expected and fluctuations in a jet. Early results are gling binaries. This was pioneered with to contribute to the study of AGN, as it very promising and call for long-term mon- AMBER and proved invaluable in model- has greater sensitivity than AMBER, par- itoring of the Galactic Centre (GRAVITY ling complex systems, such as the Wolf- ticularly in its spectrally resolved mode Collaboration, 2017a). Rayet γ2 Velorum (­Lamberts et al., 2017).

The Messenger 171 – March 2018 15 Telescopes and Instrumentation Mérand A., The VLTI Roadmap

Physical separation (au) D = 2 kpc Figure 2. A schematic 0.11.0 10.0 100.01000.010000.0 diagram to compare the angular scales associ- ated with different observing techniques

s (bottom row), binary for-

ry Dynamical interactions ion

er

ut with other cluster members mation processes (mid-

rg Binary evolution

Bina dle row) and binary evo- evol Me Single star evolution lution (top row) for hot O-type stars at a typical distance of 2 kpc. This illustrates the unique

ry ion role that the VLTI’s long Fission? Disc fragmentation through Dynamical interactions at baseline interferometry Bina rm Migration? gravitational instabilities? and capture? can play in probing disc fo fragmentation in early systems. Thanks to its unsurpassed angular resolution, VLTI imaging

y Sparse Long baseline Seeing limited is the only way to probe aperture interferometry imaging close binary systems

ometr masking in g that are interacting. rv Reproduced with per- Phot

chniqu e Speckle Adaptive optics imaging mission of H. Sana. Obse te

Spectroscopy HST/FGS Coronagraphy

0.11.0 10.0 100.01000.010000.0 Angular separation (mas)

During GRAVITY commissioning new metric central geometry, advocating for Young stellar objects phenomena were observed, including a more advanced models than the typical Young stellar objects are among the micro quasar (Petrucci et al., 2017) in 1D models and 1D morphological analysis ­targets of choice for the VLTI; the which relativistic jets could be resolved, of previous observations (Chiavassa et ­com­bination of high angular resolution and the accretion zone in a high-mass al., 2010). (~ milli-arcseconds) and the spectral X-ray binary (Waisberg et al., 2017). High- range (H- and K-bands) makes it the per- precision interferometric instruments yield PIONIER, GRAVITY and MATISSE are fect machine to study the central regions high dynamic ranges; PIONIER offers expected to continue targeting evolved of protoplanetary discs. For example, a detection limit up to a contrast of 500, stars, especially when all available wave- PIONIER recently revealed the universal- which enables the measurement of bands (from H- to N-bands) are used ity of the truncated inner-ring structures dynamical masses of unexplored stellar simultaneously. An important obstacle to in the hot dust discs of Herbig AeBe classes, such as Cepheids (Gallenne et studying mass loss so far was that stars stars via a survey of 51 objects (Lazareff al., 2015). GRAVITY is expected to reach must be resolved both spatially and tem- et al., 2017). a similar dynamic range performance porally in order to disentangle convection that, combined with its spectral resolution, and pulsation, which have timescales of GRAVITY and MATISSE are expected to will allow for a better characterisation of weeks. The availability of four-telescope continue this legacy. GRAVITY offers the companions. observations offers the possibility of unique possibility of studying winds or snapshot imaging on a timescale of a few jets thanks to its sensitive fringe tracker, Mass loss from evolved stars days, which can reveal mass loss in all its which allows observations of Brγ, He I Evolved stars play a crucial role in enrich- spatial complexity, potentially tying dust or CO lines at high spectral resolution ing their host galaxies in heavy elements. patches above the atmosphere to phe- (R ~ 4000). The gas and dust have very Little is known about the actual mass nomena at the surfaces of stars. PIONIER different dynamics in protoplanetary loss mechanisms involved since all mod- will resolve the photosphere, GRAVITY discs and play different roles in planet els underestimate mass loss rates. It is will probe the molecular wind and hot formation scenarios. believed that mass loss is linked to pulsa- dust close to the sublimation tempera- tion, convection and/or shocks in the ture, and MATISSE will resolve the oxy- GRAVITY commissioning observations upper atmosphere of dusty stars (Höfner gen- and carbon-rich dust. ALMA can of S CrA revealed a Brγ emitting region et al., 2018). The VLTI is uniquely posi- probe the larger-scale structure with H2O of r ~ 0.06 au that was located in the tioned to resolve the photospheres and and OH maser observations. SPHERE on inner gaseous disc but was twice as big dust shells around evolved stars (Fig- the VLT could also provide complemen- as the truncation radius, tracing a wind ure 3). The advent of 3D modelling and tary imaging, revealing interactions of the (GRAVITY Collaboration, 2017c). Detailed early imaging with optical interferometry mass loss with the interstellar medium modelling also indicates the presence of suggest a strong departure from a sym- (Kervella et al., 2017; Figure 3). magnetospheric accretion. The sensitivity

16 The Messenger 171 – March 2018 Degenerate C/O core Convective stellar envelope Dynamical atmosphere Circumstellar envelope ISM S. Liljengre S. Molecule Dust Molecule destruction formation formation and formation Ionisation CO, H , H O, Silicates, H OOH + HOHO + H Chemistry C/O < 1 2 2 2 OII Nucleo- TiO, VO, SiO Mg/Al-oxides S + OH SO + H synthesis CO, H , CN, Amorphous C, HCNCN + H CN C + N C/O > 1 2 CII C2, C2H2, HCN SiC CN + C2H2 HC3N

Shocks Mixing Interstellar radiation Stable outflow He & H Processes burning shells Wind acceleration Pulsation Bow shocks

~0.0001 R ~1 R ~10 R ~10000 R * * * * Figure 3. Schematic diagram of an asymptotic giant stellar and/or disc wind. The availability morphology of the dust thanks to its branch star from interior to circumstellar environ- of the full K-band will enable the study of four-telescope imaging capabilities, which ment, showing the chemical and physical processes involved in mass loss. VLTI instrumentation (PIONIER, the CO bandhead emission longward of will remove assumptions about the disc GRAVITY and MATISSE) can resolve these stars 2.3 μm. The infrared CO emission traces geometry. The VLTI will complement from their surfaces (at 1 R ) to their circumstellar * warm gas in the inner regions of proto­ ALMA, which offers similar angular scales, envelopes (out to ~ 10 R ), probing convection, pulsa- * planetary discs, potentially tracing the to draw a complete picture of the dust tion, shocks and dust formation. ALMA can resolve the circumstellar environment and molecular disc-star interactions (van der Plas et al., and gas in protoplanetary discs (Figure 4). ­processes. VLT imaging at high angular resolution 2014; Illee et al., 2014). accesses the outer scales (100–1000 R ). Repro- * duced here with permission of S. Lijengre. MATISSE will continue mineralogy studies Beyond GRAVITY and MATISSE that MIDI initiated earlier, detecting differ- of GRAVITY will allow this study to be ent types of dust at different disc radii The need for milli-arcsecond resolution extended further as the Brγ line can trace (van Boekel et al., 2004). MATISSE observations will not disappear once both the disc and the inner region of the will provide much better insights into the GRAVITY and MATISSE yield their

MIR

Scattered light

(sub-)mm Figure 4. Protoplanetary disc structure, grain evolution processes and observational con- straints for 1 2 protoplanetary discs 3 (the central star is omit- 4 ted for illustration pur- a poses). The left side b shows the dust grain d c processes, while the right side shows the area of the disc that can be probed using differ- Distance in AU ent wavelength ranges and facilities. The VLTI 110100 uniquely probes the 1 Turbulent mixing (radial or vertical) inner disc in the near 2 Vertical settling 0.35 mm0.3 mmALMA infrared (~ 2 µm using PIONIER and GRAVITY), 3 Radial drift 2 μm 10 μm VLTI and in the mid-infrared 4 a) Sticking (~ 10 µm using MAT- b) Bouncing 2 μm10 μm ELT ISSE). Adapted from c) Fragmentation with mass transfer Testi et al. (2014), with d) Fragmentation JWST/MIRI permission.

The Messenger 171 – March 2018 17 Telescopes and Instrumentation Mérand A., The VLTI Roadmap

expected treasure trove of results. We has already developed a number of capa- AMBER+FINITO, the PRIMA Fringe can already anticipate that both instru- bilities, optical interferometry still has a ­Sensor Units (used with MIDI) and now ments will open up new avenues. The considerable margin for development, as GRAVITY. VLTI should aim to be a major contributor discussed in the recent European Inter- to the following astrophysical questions ferometry Initiative report entitled “Future MATISSE requires a fringe tracker to well beyond the immediate horizons: of optical-infrared Interferometry in achieve its full scientific potential, for – Do we understand stars? Europe”1. which GRAVITY’s fringe tracker will be – How do planetary systems form? used initially. However, this might not be – How do stars enrich galaxies? The following capabilities would help to optimal and the performance of this com- – How do massive stars interact with their pursue the goals mentioned earlier: bination should be assessed a few years environment? into MATISSE operation. Building a new – How do supernova progenitors work? Imaging with a larger number of fringe tracker might be the ultimate solu- – What is the prevalence and role of stel- telescopes tion to improving performance. Improving lar multiplicity? The history of sub-millimetre arrays the facility should also help. The optical – Do we understand the immediate sur- shows that imaging complex sources can transmission not only affects the sensitiv- roundings of the Galactic Centre and become routine with arrays of seven to ity, but fringe trackers are also suscepti- strong gravity in action? eight telescopes. The VLTI is already ble to wavefront perturbations that lower – Do we understand the interactions equipped with eight telescopes (four ATs their sensitivity. Reaching the diffraction between supermassive black holes and and four UTs) and six delay lines, even limit and a Strehl ratio of more than 50 % their host galaxies? though current instrumentation (PIONIER, using adaptive optics (AO) will improve GRAVITY, MATISSE) can only combine fringe tracking sensitivity. The VLTI can develop strong synergies up to four of these at a time. Additionally, with ALMA in all of these areas. In addi- the VLTI delay line tunnels can accom­ The UTs are equipped with AO dedicated tion, the VLTI could be a significant con- modate two more delay lines. Alterna- to the VLTI with visible (MACAO) and tributor to the following areas, with the tively, the VLTI platform can host several infrared (CIAO) wavefront sensors. NAOMI, development of new capabilities and additional telescopes without major infra- the AO system for the ATs, will be exploitation of synergies: structure modifications. deployed a from now. Fringe track- – Improving the cosmological distance ers correct for atmospheric pertur­ scale, by studying Cepheids, the tip of A first step before expanding VLTI base- bations, but the UTs’ vibrations still domi- the red giant branch stars, eclipsing line capabilities is to fully exploit the nate over atmospheric turbulence. Con- binaries, stars, ­current facility. One of the current limita- tinuous efforts will be required to mitigate and other distance indicators such as tions for imaging with the ATs is the spa- and reduce the telescope vibrations in AGN. tial frequency (uv-plane coverage); the order to maintain and improve the VLTI’s – Ground-based astrometric follow up VLTI can only be offered with a maximum sensitivity and dynamic range. of exoplanet detections post-GAIA. baseline length that is 70 % of the longest – Characterisation of host stars in the possible baseline (202 m), and the possi- High dynamic range context of exoplanet and asteroseis- ble quadruplets of telescopes are limited The current dynamic range of VLTI instru- mology transit missions (for example, by their sky coverage. Extending the ments (about 1:500) limits the ability to via the PLAnetary Transits and Oscilla- delay line length could solve both issues. address some particularly exciting sci- tions of stars mission [PLATO]). Although the delay line tunnel cannot be ence cases. The advantage of a dynamic – Direct imaging of transient phenomena, extended, delay lines can have their opti- range of 1:1000 to 1:10 000 in the mid-­ such as microlensing events, detected cal path length doubled by folding the infrared (i.e., L- and M-bands) was by current and future large-scale photo- optical beam and passing twice through demonstrated at a recent workshop for a metric surveys (for example, with the the delay line cart. This would allow the new VLTI instrument project (HI-5)2. This Large Synoptic Survey Telescope longest AT baseline (202 m) to be offered, capability could lead to the direct imaging [LSST]). and increase the number of possible AT of planet formation or even young quadruplets with full sky coverage. planets.

Possible future developments Sensitive co-phasing A wealth of instrumentation developments This improves imaging by allowing the are currently underway to build high-­ It is of the utmost importance to maintain longest baselines (with lowest fringe contrast beam combiners in the L- and an active research and development ­contrast) to be used, thanks to baseline M-bands using single-mode fibres and ­programme in interferometric instrumen- bootstrapping; it also improves sensitivity integrated-optics components, which tation. Taking an example from millimetre and/or spectral resolution, in particular could lead to simple yet transformative interferometry, one can already consider when off-axis fringe tracking, or fringe visitor instruments, following in the foot- the expansion of the VLTI’s capabilities tracking in a different waveband, is imple- steps of PIONIER. The forthcoming in four areas: imaging, sensitivity, instru- mented. The VLTI is at the forefront of decommissioning of AMBER will open mentation, and astrometry. Unlike tradi- the development and operation of fringe up space for a visitor instrument. The tional single-dish instrumentation, which trackers, thanks to its experience with requirements for high dynamic range are

18 The Messenger 171 – March 2018 intimately linked to the performance of are fostered by ESO and the European References the infrastructure. Interferometry Initiative2. Chiavassa, A. et al. 2010, A&A, 511A, 51C – Organise a conference before 2020 to Gallenne, A. et al. 2015, A&A, 579A, 68G Extension to shorter wavelengths involve the community in a discussion Gonté, F. et al. 2016, SPIE, 9907, 1ZG (< 1.4 µm) of possible third-generation instru­ GRAVITY Collaboration 2017a, A&A, 602, A94 The main driver for such an extension mentation and upgraded infrastructure GRAVITY Collaboration 2017b, The Messenger, 170, 10 would be the improvement in spatial res- for VLTI. GRAVITY Collaboration 2017c, A&A, 608, 78 olution, opening up the domain of stellar Höfner, S. & Olofsson, H. 2018, A&ARv, 26, 1 surface imaging of stars, Epoch 2: 2020–2025 Hönig, S. 2016, AASL, 439, 95 which remains mostly unexplored. A visi- – Fully exploit the existing infrastructure by Ilee, J. D. et al. 2014, MNRAS, 445, 3723 Kervella, P. et al. 2017, The Messenger, 167, 20 ble-light instrument with high spectral upgrading the existing instrumentation. Lamberts, A. et al. 2017, MNRAS, 468, 2655L resolution would be able to resolve veloc- – Increase sky coverage and angular Lazareff, B. et al. 2017, A&A, 599A, 85L ity fields, such as rotation or pulsation, at ­resolution by doubling the delay line Lopez, B. et al. 2014, The Messenger, 157, 5 the surface of stars. Other science cases optical path. Matter, A. et al. 2016, SPIE, 9907, 0AM Petrucci, P.-O. et al. 2017, A&A, 602L, 11G and instrumentation developments are – Host visiting instruments to push Pribulla, T. et al. 2011, A&A, 528A, 21 detailed in the recent white book Science ­interferometric techniques in new Rakshit, S. 2015, MNRAS, 447, 2420R Cases for a Visible Interferometer (Stee directions. Sana, H. et al. 2014, ApJS, 215, 15S et al., 2017), showing the growing interest Stee, P. et al. 2017, arxiv1703.02395 Testi, L. et al. 2014, Protostars and Planets VI, ed. from the community. Such developments Epoch 3: beyond 2025 Beuther, H., Klessen, R., Dullemond, C. & would require not only new instrumenta- – VLTI imaging capability might be ­Henning, T., (Tucson: University Arizona Press), tion, but also significant facility upgrades, expanded by adding more telescopes 339 since the VLTI only transmits near- and and building a six- to eight-telescope Tristram, K. R. W. et al. 2014, A&A, 563, 82 van Boekel, R. et al. 2004, Nature, 432, 479V mid-infrared light to the delay lines and beam combiner, driven by the ability van der Plas, G. et al. 2014, A&A, 574, 75 laboratory, leaving the shorter wavelengths of the community to propose strong Waisberg, I. et al. 2017, ApJ, 844, 72W at the telescopes for guiding purposes. science-driven projects. Wittkowski, M. et al. 2004, A&A, 418, 39 – The VLTI could be used as a develop- Woillez, J. et al. 2016, SPIE, 9907, 06W Weigelt, G. et al. 2012, A&A, 541, L9 The roadmap for the VLTI, recommended ment platform for next-generation Weigelt, G. et al. 2016, A&A, 594A, 106 in October 2017 by ESO’s Scientific and ­optical interferometers. Technical Committee4, can be divided into three epochs: This roadmap aims to pave the way for Links future VLTI developments at ESO, as 1 Working group on the future of interferometry in Epoch 1: until 2020 well as to encourage the community to Europe: http://www.european-interferometry.eu/ – Make GRAVITY and MATISSE a suc- drive the long-term future of the VLTI. working-groups/the-future-of-interferometry-in-­ cess by providing an efficient, optimally europe 2 Hi-5 Kickoff Meeting website: scheduled VLTI array. Demonstrate http://www.biosignatures.ulg.ac.be/hi-5 robust fringe tracking and increase Acknowledgements 3 The European Interferometry Initiative: sensitivity. www.european-interferometry.eu/ I would like to thank Jean-Philippe Berger who 4 – Expand the VLTI user base by improv- ESO Scientific Technical Committee report on started this prospective exercise before leaving ESO VLTI Roadmap STC-599: https://www.eso.org/ ing accessibility to non-experts, possi- in the summer of 2016. public/about-eso/committees/stc/stc-90th/public/ bly through dedicated VLTI centres that STC_599_VLTI_Roadmap_90th_STC_mtg_ Oct_2017.pdf ESO/MATISSE consortium ESO/MATISSE

Complex optics on the MATISSE instrument on the VLTI. Many components are repeated four times, one for each beam of light being fed into the instru- ment.

The Messenger 171 – March 2018 19 Telescopes and Instrumentation DOI: 10.18727/0722-6691/5064

The ELT in 2017: The Year of the Primary Mirror

Michele Cirasuolo1 Background: how the ELT works Translated into astrophysical terms this Roberto Tamai1 means opening up new discovery spaces Marc Cayrel1 The optical design of the ELT is based — from close to their stars, Bertrand Koehler1 on a novel five-mirror scheme capable of to black holes, to the building blocks of Fabio Biancat Marchet1 collecting and focusing the light from galaxies — both in the local Universe Juan Carlos González1 astronomical sources and feeding state- and billions of light years away. Specific Martin Dimmler1 of-the-art instruments to carry out imag- examples include the ability to detect Mauro Tuti1 ing and spectroscopy. As shown in Fig- and characterise extra-solar planets in & the ELT Team ure 1, the light is collected by the giant the habitable zone around our closest primary mirror (39.3 metres in diameter), star Proxima Centauri, or to resolve giant relayed via the secondary and tertiary molecular clouds (the building blocks 1 ESO mirrors, M2 and M3 (both of which have of star formation) down to ~ 50 pc in dis- ~ 4-metre diameters), to M4 and M5 (the tant galaxies at redshift z ~ 2, and even core of the telescope adaptive optics). smaller structures for sources that are The Extremely Large Telescope (ELT) The light then reaches the instruments on gravitationally lensed by foreground clus- is at the core of ESO’s vision to deliver one of the two Nasmyth platforms. ters, all with unprecedented sensitivity. the largest optical and infrared tele- scope in the world. With its unrivalled This design provides an unvignetted field sensitivity and angular resolution the of view (FoV) with a diameter of 10 arc- The giant primary mirror ELT will transform our view of the Uni- minutes on the sky, or about 80 square verse: from exoplanets to resolved stel- arcminutes (i.e., ~ 1/9 of the area of the One of the many technological marvels lar populations, from galaxy evolution full moon). Thanks to the combined acti- of ESO’s ELT is the primary mirror, M1, to cosmology and fundamental physics. vation of M4 and M5, it will have the along with all the necessary infrastructure This article focuses on one of the most capability to correct for atmospheric tur- and control schemes that are needed to challenging aspects of the entire pro- bulence as well as the vibration of the make it work. At 39.3 metres in diameter gramme, the 39-metre primary mirror ­telescope structure induced by its move- it will be the largest optical/infrared tele- (M1). 2017 was a particularly intense ment and the wind. This is crucial to scope ever built. Of course, this comes year for M1, the main highlight being the allow the ELT to reach its diffraction limit, with attendant challenges. The mirror is approval by ESO’s Council to proceed which is ~ 8 milli-arcseconds (mas) in segmented, being made of 798 quasi- with construction of the entire mirror. In the J-band (at λ ~ 1.2 μm) and ~ 14 mas hexagonal mirrors, each of which is about addition, several contracts have been in the K-band, thereby providing images 1.45 metres in size (corner-to-corner), is placed to ensure that the giant primary 15 times sharper than Hubble Space only 50 mm thick and weighs 250 kg. The mirror will be operational at first light. Telescope. full M1 has a six-fold symmetry; there are

Figure 1. This diagram shows the novel five- mirror optical system of ESO’s ELT. Before it can reach the ELT’s scientific instruments, light is first reflected from the tele- scope’s giant concave 39-metre segmented primary mirror (M1), after which it bounces off two further four-metre-class mirrors, one convex (M2) and one concave (M3). The final two mirrors (M4 and M5) form a built-in adaptive optics system to allow extremely sharp images to be formed at the final focal plane.

20 The Messenger 171 – March 2018 Figure 2. One segment support structure of the giant primary mirror of the ELT undergoing

Henri Werij/TNO Henri testing.

six identical sectors of 133 segments face. The load on the whiffletree can be ESO Council approval of the full M1 each. In each sector all 133 segments are adjusted via warping harnesses so as different from each other in shape and to slightly change the shape of the mirror When the construction of the ELT was optical prescription; in other words there to compensate for optical aberrations approved by Council in December 2014, are 133 different segment types. In order induced by gravity and thermal effects it was split into two phases. Phase 1 to facilitate recoating there will be a sev- (see Figure 2). Moreover, each segment was for the 39-metre ELT with the Multi- enth sector with 133 segments, i.e., one assembly can be moved in height AO Imaging CAmera for Deep Observa- for each segment type. This adds up to a and tip/tilt relative to the structure by tions (MICADO), the High Angular Resolu- grand total of 931 segments. using three positioning actuators (PACTs). tion Monolithic Optical and Near-infrared These three actuators can move inde- Integral field spectrograph (­HARMONI) M1 is evidently a very complex system. pendently with an accuracy of 2 nm with and the Mid-infrared ELT Imager and Therefore, to achieve the required scien- a maximum excursion (or stroke) of Spectrograph (METIS) instruments and tific performance, it needs to be main- 10 mm to adjust its position and maintain the Multi-conjugate Adaptive Optics tained in position and be phased to an the perfect co-alignment of all the seg- RelaY (MAORY) adaptive optics module. accuracy of tens of nanometres — 10 000 ments and effectively create a giant mon- The Phase 1 ELT was still capable of times thinner than a human hair — across olithic mirror. To achieve this, each side of achieving breakthrough discoveries, its entire 39-metre diameter! This is each hexagonal segment has two “edge although it excluded a number of critical extremely challenging, as the full struc- sensors” that constantly measure piston, components, notably the five inner rings ture will be moving constantly during gap and shear with respect to the adja- (Figure 3), the seventh sector of segments an observation, and will be affected by cent segment to nanometre accuracy for M1, and one of the facilities needed wind and thermal changes. and provide the necessary information to to maintain the quality of the M1 coating. the control system to activate the PACTs, The intention was to include these items There are various ways in which M1 can allowing the segments to work together in a second phase of construction at a be actively controlled. Each segment, to form a perfect imaging system. later date. made of the low-expansion ceramic mate- rial Zerodur© (from SCHOTT), is sup- All in all, the M1 is a colossal system, fea- ESO’s management and governing ported on a 27-point whiffletree, which is turing a staggering 798 segments, almost ­bodies always recognised the critical a mechanism to evenly distribute the 2500 PACTs and about 9000 edge sen- importance of these Phase 2 items. support across the back of the segment sors (4500 pairs), not including the sev- Hence, at its December 2017 meeting, using 27 points of contact across its sur- enth sector and the spares. following positive recommendations from

The Messenger 171 – March 2018 21 Telescopes and Instrumentation Cirasuolo M. et al., The ELT in 2017: The Year of the Primary Mirror

Figure 3. Left: Sche- matic graph comparing the Phase 1 M1 (top) without the 5 inner rings, i.e., only 588 mirrors and a large central obscuration, and the full M1 as now approved by ESO Council (bottom) with 798 segments, including the Phase 2 segments. Right: A view of M1, once it is mounted on the main structure. ESO/L. Calçada/ACe Consortium Calçada/ACe ESO/L. the external ELT Management Advisory (see Figure 3), which improves the ability ment supports, PACTs, edge sensors, Committee (EMAC) and from ESO’s stat- to control the shape of the mirror surface. and the M1 Control System. utory advisory bodies, the Scientific and Filling the gap and reducing the linear Technical Committee (STC) and Finance obscuration is also very important for the All major contracts related to these com- Committee (FC), the ESO Council gave ELT’s ultimate performance as it is easier ponents of M1 have been approved, its authorisation to exercise contractual to concentrate light on science detectors signed and initiated, except for the series options to procure the previous unfunded with a smaller central obscuration; the production of M1 segment supports, Phase 2 items related to M1 (i.e., the five peak of the point spread function (PSF) the contract for which is expected to be inner rings, the seventh sector and the is a factor of two higher. This means awarded in early 2018. The timely initia- second M1 maintenance unit). This deci- that the energy is more focused, further tion of all of these contracts is particularly sion enables the highest possible science increasing sensitivity and improving the important for two reasons: first, M1 fabri- return for users and for instrumentation, adaptive optics performance and sky cation lies on the so-called critical path lowers the risk to the programme and coverage. A smaller central obscuration for the ELT, meaning that any delay would lowers the final cost of the full ELT. Indeed, is particularly important for the study of have a direct impact on the date of first if M1 segment production were to be exoplanets using the technique of high- light; second, these contracts are inter- stopped after Phase 1 between 2019 and contrast imaging: the better the PSF the dependent. For example, the blank is 2020, the costs involved in restarting the easier it is to suppress the light from the required to start the polishing, and the production of the blanks, segment pol­ much brighter central star and to detect segment support is required at the end of ishing and the mirror supports at a later planets that are close to the star, thereby the polishing process for final testing and date would almost certainly be prohibitive, making the goal of directly observing ion-beam figuring. especially if the same stringent tolerances Earth analogues attainable. had to be maintained after (potentially) As 2017 was such a successful year for reopening and refurbishing the produc- procurement, we can provide some details tion facilities. Making the M1 mirror about the major contracts involved. In a ceremony held in January 2017, a con- The full M1, including the inner five rings, Now that the ESO Council has approved tract was signed for the production of the has clear advantages regarding scientific the construction of the full M1, procure- edge sensors with FAMES, a consortium return. It expands the collecting area of ment and production of the various com- composed of Fogale (France) and Micro- the primary mirror by 36 % compared to ponents of M1 are going ahead. Indeed, Epsilon (Germany), together with three the Phase I configuration, which increases 2017 is known as “the year of M1” within other ELT procurements (the M2 and M3 its sensitivity (i.e., its capability to efficiently the ELT project, reflecting the many steps Cells with SENER and the blanks for M2 collect light from fainter and/or more dis- that were taken towards the fabrication and M3 with SCHOTT). The contract with tant sources). It reduces the linear size of of the various M1 components, including FAMES covers the design and fabrication the central hole by nearly a factor of two segment blanks, segment polishing, seg- of a total of approximately 9000 edge

22 The Messenger 171 – March 2018 Figure 4. This image shows the first cast from which six blanks will be obtained by SCHOTT (Germany) at their facility in Mainz. This first cast is a thick cylinder

SCHOTT/ESO that will be cut into six slices, each of which will become a segment blank.

test bench to develop and validate the telescope wavefront control algorithms.

This is only a fraction of the impressive amount of work going on, both at ESO and at the various industrial partners, towards the efficient, accurate and timely manufacturing of all the various compo- nents that will make up the ELT.

The life of the M1 mirror

It should be noted that the manufactur- ing, assembly and installation of M1 only represent its first steps, as M1 will lead a sensors (~ 4500 pairs) for the 798 hexag- blanks will then be delivered by SCHOTT life that requires constant reconfiguration. onal segments of M1. These sensors are to Reosc to figure and polish the seg- Indeed, to maintain the best reflectivity the most accurate to ever be used in a ments, cut them into hexagonal shapes, and sensitivity of the telescope, each telescope and can measure the relative integrate them into their support systems, ­mirror will need to be recoated every 18 positions of the segments to an accuracy and perform optical tests before delivery months, like the mirrors of the VLT. Given of a few nanometres. The challenge in to Chile. During the polishing process, the number of segments, this means this case is two-fold — the sensors must each segment will be polished until it has removing, recoating and reinstalling two reliably provide the required precision, no surface irregularity greater than about segments on the telescope every day for and production must proceed at an 8 nm. To meet the challenge of delivering the entire lifetime of the telescope. This appropriate pace to deliver thousands of such a large number of polished seg- represents a significant logistical effort, in sensors by the specified deadline. ments within seven years, Safran Reosc order to keep up an efficient stripping, will build up to a peak production rate washing and coating process, as well as At a joint signature ceremony at the end of one mirror a day. To meet this demand, a well-defined maintenance plan for the of May 2017, two important contracts Safran Reosc has already begun the thousands of ELT components. For this were signed to produce the 798 segments ­necessary refurbishment of a facility at reason, the seventh sector of segments for the M1. The first one was signed with their Poitiers plant. The contract for the and the second maintenance unit (includ- SCHOTT (Germany) for the production of segment polishing is the second-largest ing the washing, stripping and coating the blanks. The second one was signed contract for the construction of the ELT, plants) are particularly crucial for manag- with Safran Reosc (France) for the polish- after the one for the dome and telescope ing the efficient recoating of segments ing of the blanks and their integration structure, which was awarded to the without regularly creating temporary with the segment supports. These are Ace Consortium in May 2016. It is also holes in M1. This ensures optimal mirror two of the most prominent companies the third-largest contract ESO has ever control and image quality at the lowest involved in European astronomy, and the signed. operational costs, especially for the most ceremony was a great occasion for their demanding extreme adaptive optics teams and the ESO management involved In June 2017, ESO also signed a contract applications. in the project to meet and shake hands, with the company Physik Instrumente effectively forming a partnership and GmbH & Co. KG (Germany) to manufac- The M1 mirror is certainly one of the most becoming part of a larger “family” work- ture the PACTs, which will continuously challenging sub-systems of the entire ing together to build ESO’s ELT. adjust the positions of the 798 hexagonal ELT Programme. It comprises thousands segments of M1 on the telescope struc- of highly sophisticated components that Production has already started, and in ture. Apart from the external contracts, require extreme accuracy, not only during January 2018, the first six segment blanks M1 also requires a significant amount of their manufacture, but also during instal- were successfully cast by the German work internally at ESO; in October 2017, lation and observations. This is certainly a company SCHOTT at their facility in Mainz the final design review of the M1 Local challenge and the ELT Team is closely (Figure 4). After casting, the mirror seg- Control System (LCS) was completed and following the development of all the M1 ment blanks will go through a process of there is now a focus on building a critical components to ensure the ELT’s first light slow cooling and heat treatment. The in 2024.

The Messenger 171 – March 2018 23 Image of filamentary structure in a giant molecular cloud in the Orion Nebula. Millimetre (red) and infrared (blue) observations taken with ALMA, IRAM and HAWK-I reveal high- density material down to 0.009 par- sec (2000 au) scales. The image is oriented so that north-south runs from the top right to the lower left. Astronomical Science ESO/H. Drass/ALMA (ESO/NAOJ/NRAO)/A. Hacar (ESO/NAOJ/NRAO)/A. Drass/ALMA ESO/H.

24 The Messenger 171 – March 2018 Astronomical Science DOI: 10.18727/0722-6691/5065

Exploring the Sun with ALMA

Timothy S. Bastian1 18 Space Vehicles Directorate, Air Force and to gain an understanding of how Miroslav Bárta2 Research Laboratory, Albuquerque, mechanical and radiative energy are Roman Brajša3 USA transferred through that atmospheric Bin Chen4 19 National Astronomical Observatories, layer. Bart De Pontieu5, 6 Chinese Academy of Sciences, Beijing, Dale E. Gary4 China Much of what is currently known about Gregory D. Fleishman4 the chromosphere has relied on spectro- Antonio S. Hales1, 7 scopic observations at optical and ultra- Kazumasa Iwai8 The Atacama Large Millimeter/submilli- violet wavelengths using both ground- Hugh Hudson9, 10 meter Array (ALMA) Observatory opens and space-based instrumentation. While Sujin Kim11, 12 a new window onto the Universe. The a lot of progress has been made, the Adam Kobelski13 ability to perform continuum imaging interpretation of such observations is Maria Loukitcheva4, 14, 15 and spectroscopy of astrophysical phe- complex because optical and ultraviolet Masumi Shimojo16, 17 nomena at millimetre and submillimetre lines in the chromosphere form under Ivica Skokić2, 3 wavelengths with unprecedented sen­ conditions of non-local thermodynamic Sven Wedemeyer6 sitivity opens up new avenues for the equilibrium. In contrast, emission from Stephen M. White18 study of cosmology and the evolution the Sun’s chromosphere at millimetre Yihua Yan19 of galaxies, the formation of stars and and submillimetre wavelengths is more planets, and astrochemistry. ALMA also straightforward to interpret as the emis- allows fundamentally new observations sion forms under conditions of local 1 National Radio Astronomy Observatory, to be made of objects much closer to ­thermodynamic equilibrium and the Charlottesville, USA home, including the Sun. The Sun has source function is Planckian. Moreover, 2 Astronomical Institute, Czech Academy long served as a touchstone for our the Rayleigh-Jeans approximation is valid of Sciences, Ondřejov, Czech Republic understanding of astrophysical pro- (hn/kT << 1) and so the observed intensity 3 Hvar Observatory, Faculty of Geodesy, cesses, from the nature of stellar interi- at a given frequency is linearly propor- University of Zagreb, Croatia ors, to magnetic dynamos, non-radiative tional to the temperature of the (optically 4 Center for Solar-Terrestrial Research, heating, loss, and ener- thick) emitting material. By tuning across New Jersey Institute of Technology, getic phenomena such as solar flares. the full suite of ALMA’s frequency bands Newark, USA ALMA offers new insights into all of it is possible to probe the entire depth of 5 Lockheed Martin Solar & Astrophysics these processes. the chromosphere. Lab, Palo Alto, USA 6 Rosseland Centre for Solar Physics, Wedemeyer et al. (2016) comprehensively University of Oslo, Norway ALMA solar science discuss the potential of ALMA in this 7 Joint ALMA Observatory (JAO), ­context. In brief, observations of thermal ­Santiago, Chile Radiation from the Sun at millimetre and emission from material at chromospheric 8 Institute for Space-Earth Environmental submillimetre wavelengths largely origi- temperatures will be a mainstay of Research, Nagoya University, Japan nates from the chromosphere, the rela- ALMA’s solar physics programme. Multi- 9 School of Physics and Astronomy, tively thin interface between the radia- band, high-resolution, time-resolved ­University of Glasgow, Scotland, UK tion-dominated photosphere and the observations of the chromosphere at milli­ 10 Space Sciences Laboratory, University magnetically dominated corona. The chro- metre and submillimetre wavelengths of California, Berkeley, USA mosphere is highly dynamic in nature as with ALMA will play a key role in con- 11 Korea Astronomy and Space Science magnetohydrodynamic (MHD) waves straining models of chromospheric and Institute, Daejeon, Republic of Korea propagate up from the photosphere below coronal heating. 12 University of Science and Technology, and form shocks that dissipate their Daejeon, Republic of Korea energy (for example, Wedemeyer, 2016). In addition, ALMA will be important for 13 Department of Physics and Astronomy, addressing puzzles associated with West Virginia University, Morgantown, The chromosphere remains an out­ solar filaments and prominences that USA standing problem in solar physics and, form along magnetic neutral lines. 14 Max-Planck-Institut für Sonnensystem- by extension, stellar physics. The central Although they are at chromospheric tem- forschung, Göttingen, Germany question is: why does the Sun’s atmos- peratures, they occur at coronal heights 15 Astronomical Institute, St. Petersburg phere increase in temperature above the and are therefore immersed in much University, Russia visible photosphere as one proceeds up ­hotter plasma. Quiescent prominences 16 National Astronomical Observatory of through the chromosphere and into the can remain stable for days or even weeks Japan (NAOJ), Tokyo, Japan corona? What are the heating mecha- but may then become unstable and 17 Department of Astronomical Science, nisms? How is energy transported? What erupt. ALMA offers new insights into the The Graduate University for Advanced is the role of the magnetic field? ALMA thermal structure and dynamics of Studies (SOKENDAI), Tokyo, Japan is needed to help establish the thermo­ ­prominences, their formation, and their dynamic structure of the chromosphere eventual loss of equilibrium.

The Messenger 171 – March 2018 25 Astronomical Science Bastian T. S. et al., Exploring the Sun with ALMA

ALMA observations of non-thermal emis- tion, yet considerable work was needed shape and increased side lobes. There- sion will also be of crucial importance. in practice to implement solar observing fore, while solar filters will be needed for Although observations of small flares or modes — work that is still ongoing. Provi- observations of stronger solar flares, small eruptive events may be observed sions were made to ensure that ALMA the second approach was developed for using the existing modes described antennas could safely point at the Sun quiet Sun programmes. below, observations of solar flares are not without damaging the extremely precise yet feasible with ALMA in general. Unlike telescope hardware; in particular, the sur- Yagoubov (2013) pointed out that the quiescent solar emission, solar flares face panels were chemically roughened ALMA superconductor-insulator-super- ­produce intense non-thermal radiation as in order to scatter optical and infrared conductor (SIS) mixers could be de-tuned a result of energetic electrons interacting radiation and reduce the radiative heating or de-biased to reduce the mixer gain with the local magnetic field. ALMA will of the sub-reflector and other elements and effectively increase the level at which be sensitive to emission from the most to safe levels. However, there are addi- receivers saturate, thereby allowing solar energetic of these electrons. An impor- tional factors to consider when observing observing without the use of the solar tant discovery by Kaufmann et al. (2004) the Sun. While ALMA’s sensitive receivers ­filters. This idea is illustrated in Figure 1, is that some flares produce a spectral are not damaged by pointing at the Sun, which shows the SIS current gain (left component at millimetre/submillimetre they saturate when such an intense signal axis) and conversion gain (right axis) plot- wavelengths with an inverted spectrum is introduced into the system, resulting in ted against the voltage bias for ALMA — the so-called “sub-terahertz” com­ a strongly non-linear performance. Band 3. The normal voltage bias tuning is ponent, which is distinct from the non- on the first photon step where the gain thermal gyrosynchrotron component. There are two approaches to mitigating conversion is a maximum. However, the Krucker et al. (2013) discuss it at length, the problem: attenuate the signal intro- mixer still operates at other voltage bias yet the origin of the sub-terahertz flare duced into the receiver, or increase the settings. These produce lower conver- component remains unknown. ALMA “headroom” of the receiver to ensure that sion gain but, since the dynamic range will play a central role in understanding its response remains linear by reducing scales roughly inversely with gain, these its origin. the receiver gain. Both approaches are settings can handle larger signal levels possible with ALMA. The first approach before ­saturating. This operational mode Each of these broad science themes was implemented through the use of a is referred to as the mixer de-biased (MD) additionally informs the burgeoning field solar filter on the ALMA Calibration Device. mode. Observing both the source and of “Space Weather”, which is aimed at The solar filter attenuates the incident calibrators in a specific MD mode obviates understanding the drivers of disturbances signal by a frequency-dependent amount the need to explicitly measure the change in the solar corona and wind and their that allows solar observations in a given in system gain introduced by the mode. effects on Earth and the near-Earth frequency band. However, solar filters environment. have a number of undesirable properties Another consideration, however — for mapping the quiet (i.e., non-flaring) regardless of whether the solar filter or Sun: they greatly reduce the sensitivity the MD mode is used — is that the input Enabling solar observing with ALMA with which calibrator sources can be ob­­ power changes significantly as the anten- served; they cause frequency-dependent nas move from the (solar) source to a Building on preliminary work performed complex gain changes; and they intro- ­calibrator and back. Signal levels must in East Asia, Europe, and by the Joint duce significant wavefront errors into the remain within nominal limits along the ALMA Observatory, the Solar Develop- illumination pattern of the antenna, which path to the analogue-to-digital converters ment Team was formed in late 2013, sup- result in distortions to the antenna beam and the correlator. Stepped attenuators ported by the National Science Founda- tion, ESO and East Asia. Its aims were to enable solar observations with ALMA. 250 5 LSB Superconducting gap voltage The work is supported by an extensive USB science simulations effort — the Solar 200 0 Simulations for the Atacama Large Milli- B)

metre Observatory Network (Wedemeyer (d

et al., 2015). For example, Heinzel et al. (μA) 150 –5 gain Figure 1. Plot of SIS cur-

t (2015) simulated high-resolution obser­ First photon step rent and conversion gain below the gap vations of fine structures in solar promi- rsion as a function of voltage curren setting for ALMA Band 3 nences at millimetre wavelengths. Exten- 100 Second photon step –10 nve at a local oscillator fre- SI S sive testing and validation were carried below the gap co Second photon step quency of 100 GHz. The out in 2014 and 2015, leading to the below the gap SI S arrowed ellipses indicate acceptance of solar observing with ALMA 50 First photon step –15 the relevant ordinate: left in Cycle 4 (see below). below the gap for the SIS current and right for the conversion 0 –20 gain. See Shimojo et al. Support for solar science was part of the 5678910 11 12 13 14 15 16 (2017a) for additional ALMA science programme from its incep- SIS voltage (mV) details.

26 The Messenger 171 – March 2018 are used for this purpose. A concern was Figure 2. Example of the whether the variable attenuators them- l = 30 ­double-circle pattern used to 1000 perform single-dish fast-scan selves would introduce unacceptable total power maps of the solar (­differential) phase variation between the disc, with a map spacing of source and calibrator settings, thereby 30 arcseconds. The dotted line corrupting phase calibration referenced indicates the solar limb (radius 500 960 arcseconds). The rainbow against suitable sidereal calibrators. A ) colour variation indicates the second concern was whether there are progress of the pointing pattern with time and the dashed differences between the spectral window seconds bandpass response between source and rc line indicates the track of the (a 0 centroids of the individual calibrator scans as a result of attenuator ew minor circles in the pattern. vi settings. It is a testament to the system See White et al. (2017) for addi- design that neither concern proved to d of tional details. Fiel be a significant issue. Extensive testing –500 in 2014 showed that the different attenu- ator settings used to observe calibrator sources and the Sun do not introduce significant phase errors or distort the fre- –1000 quency bandpass. MD observing modes were therefore adopted as the basis for –1000 –500 0 5001000 observations of the quiet Sun. Field of view (arcseconds)

Two additional challenges are posed by correlator. In order to recover the Sun’s particularly important on long interfero- solar observations. First, the complex brightness distribution on the largest metric baselines for correcting differential brightness distribution of the Sun contrib- angular scales, all interferometric obser- phase variations. Unfortunately, the WVRs utes significant power on angular scales vations were supplemented by full-disc saturate when ALMA’s antennas are ranging from sub-arcsecond scales to fast-scan total power maps (Phillips et pointed at the Sun and WVR measure- the diameter of the solar disc, the details al., 2015) in the relevant frequency bands ments are therefore unavailable for solar of which vary on short timescales (tens (Figures 2 and 3). These can be combined observations. As a consequence, obser- of seconds). Good instantaneous sam- with the interferometric data via “feather- vations of the Sun with long-baseline pling of the aperture plane is needed to ing” to produce photometrically accurate antenna configurations cannot currently recover measurements over the full range maps of the Sun’s brightness distribution. be supported. of angular scales. The 7-metre antennas in the fixed Atacama Compact Array were Second, water vapour radiometers The extensive solar development efforts therefore included as well as those in the (WVRs) are used on each ALMA antenna required to bring solar observing modes 12-metre array so as to sample a broader to measure variations in the electrical to the solar community are documented range of angular scales. All antennas path length introduced by the overlying in two papers. Shimojo et al. (2017a) dis- were processed through the baseline atmosphere. These measurements are cuss the steps necessary to implement

Figure 3. Left: Example of a full-disc fast-scan total power map in Band 9 (0.45 mm) on 18 December 2015 using a scan pattern similar to that shown in ­Figure 1. Right: The corre- sponding image in Ha.

The Messenger 171 – March 2018 27 Astronomical Science Bastian T. S. et al., Exploring the Sun with ALMA

Figure 4. Right: A white-light continuum image of add tremendous scientific value to ALMA to correct for the Sun’s differential the Sun obtained by the Helioseismic and Magnetic observations. For Cycle 4, these include rotation. Imager on board the Solar Dynamics Observatory showing a sunspot imaged by ALMA. Centre: A detail the Interface Region Imaging Spectro- of the same. Left: Map of the sunspot in Band 6 graph (IRIS; De Pontieu et al., 2014), which An observing strategy that mitigates, in (1.25 mm). The map was formed by a mosaic of 149 is led by NASA and operates at ultraviolet part, some of the complexity associated individual antenna pointings. The data were acquired wavelengths, and the Hinode mission, with scheduling solar programmes is to as part of science verification on 18 December 2015. See Shimojo et al. (2017) for additional details. which is led by the Japan Aerospace execute them during an “observing cam- Exploration Agency (JAXA) in cooperation paign”. That is, in coordination with rele- with NASA, the UK Science and Technol- vant missions and telescopes, a fixed interferometric imaging of the Sun, and ogy Facilities Council (STFC), ESO, and window of time is designated in one or White et al. (2017) describe fast-scan total the Norwegian Space Centre (Kosugi et more antenna configurations during which power mapping of the Sun. Examples of al., 2007), and which operates at optical, the bulk of the ALMA solar observing is maps obtained by ALMA during science extreme ultraviolet (EUV), and soft X-ray discharged. This worked well for Cycle 4 verification are shown in Figures 3 and 4. wavelengths. Numerous ground-based observing programmes from an opera- optical telescopes also participated. tional standpoint, although the commu­ nication strategy between the ALMA ALMA Cycle 4 Emission from the Sun can change dra- ­Principal Investigator, the ALMA duty matically on short timescales. Even so- astronomer and ALMA operations needs Solar observing was first made available called “quiet” Sun emission from non-­ further refinement. to the community in Cycle 4 with the call flaring active regions may evolve signifi- for proposals in March 2016. Cycle 4 solar cantly over the course of a day. Meeting programmes were restricted to continuum the science goals of a particular pro- Early science observations in two frequency bands, gramme may therefore pose operational Band 3 (3 mm) and Band 6 (1.25 mm) and scheduling challenges. The need to ALMA science verification data were using MD mode observing. Since WVR respond quickly to changing targeting released to the community in January measurements are not possible, solar requests is of paramount importance. In 2017 3, 4. These data4 validated solar observing programmes were further order to image a specific target on the observing modes released to the com- restricted to the use of the three most Sun, ALMA must correctly track the munity for Cycle 4 observing and have compact 12-metre antenna configurations Sun’s physical ephemeris, offsets relative served as the basis for a number of (C40-1, C40-2, and C40-3). Using C40-3, to the physical ephemeris, and its rota- recent scientific papers. Several studies the maximum possible angular resolutions tion. ALMA can accommodate observa- made full use of the interferometric and for Bands 3 and 6 were approximately tions of ephemeris objects such as the fast-scan total power data and others 1.5 arcseconds and 0.63 arcseconds, Sun through user-provided files that made use of the superb fast-scan total respectively. specify the exact target coordinates as power maps of the full disc of the Sun a function of time. A convenient tool, the alone: Nearly 50 solar proposals were received ALMA solar ephemeris generator — in Cycle 4 and roughly a third of these based on the Jet Propulsion Laboratory – Shimojo et al. (2017b) studied the erup- were approved and allocated observing (JPL) HORIZONS web interface1, 2 — was tion of a plasmoid in a solar active time at priority A or B. The solar physics developed by Ivica Skokić to generate region jointly at 3 mm, in the EUV (Solar community is inherently multi-wavelength files like these quickly. A solar observer Dynamics Observatory) and in soft in practice. A wide variety of ground- and can now specify the target offset relative X-rays (Hinode), demonstrating the space-based assets are available that to the centre of the Sun, and use a model ­utility of both the time-resolved, snap-

28 The Messenger 171 – March 2018 shot imaging capabilities of ALMA and Sun’s millimetre radiation in comparison magnetic fields. Ultimately, measurements the use of multi-wavelength observa- with the chromospheric and coronal of Stokes V (circular polarisation) to a tions to constrain the properties of the emission seen at optical and EUV wave- ­precision of 0.1 % are needed to fully plasmoid. lengths, finding a high degree of corre- exploit polarimetric observations of the lation, even including millimetre coun- Sun. Details of how solar polarimetric – Bastian et al. (2017) compared ALMA terparts to coronal X-ray bright points. observations will be exploited and the 1.25-mm observations of an active requirements for ALMA are discussed by region with the corresponding observa- These early results already anticipate the Loukitcheva et al. (2017b). tions of the Mg II ultraviolet emission richness and diversity of the solar obser- made by IRIS. The ALMA data com- vations to come under regular observing. Imaging spectroscopy prised a 149-point mosaic of a solar With the support of additional frequency Support for spectral-line-mode observing active region that was feathered with bands and new capabilities, the breadth is required to detect and exploit obser­ the corresponding fast-scan total of solar science that can be addressed vations of radio recombination lines power map. Although believed to form by ALMA will be fully realised. We con- (RRLs) and, possibly, other atomic and at similar heights in the chromosphere, clude with a brief discussion of future molecular transitions in the solar atmos- there are distinct differences between capabilities for solar observing. phere. Clark et al. (2000a, b) reported line the millimetre brightness temperature widths of order 500 MHz for the hydro- and the ultraviolet radiation tempera- gen RRLs H21a and H19a, suggesting ture, which are attributed to regional Future capabilities that relatively low-­resolution “time division dependencies of the formation height mode” obser­vations with ALMA may be and/or an increased degree of coupling To date, ALMA has barely scratched sufficient for early exploitation of RRLs. between the ultraviolet source function the surface of the scientific potential of and the local gas temperature in hotter millimetre and submillimetre observations Solar flares and denser areas of the active region. of the Sun. In addition to analysing and The strategy employed for observing the publishing the wealth of results from quiet Sun in Bands 3 and 6 using the MD – Iwai et al. (2017) discovered a signifi- Cycle 4 observations in Bands 3 and 6, receiver modes will not be feasible for cant 3-mm brightness enhancement in much work remains to enable observa- solar flares, which can produce intense the centre of a sunspot umbra that is tions in additional frequency bands and radiation that far exceeds the ubiquitous coincident with enhancements in the to deploy new observing modes. These, thermal background of the solar chromo- 1330 Å and 1400 Å ultraviolet contin- in turn, will allow the full power of ALMA sphere. For solar flare observations solar uum images observed by IRIS. The to be brought to bear on the fundamental filters must be used. The East Asia team enhancement may be intrinsic to sun- science questions outlined above. has previously demonstrated the use of spot umbrae at chromospheric heights, solar filters for flare observations but or alternatively could be the millimetre Additional frequency bands detailed calibration procedures have yet counterpart to a polar plume. The frequency range sampled by ALMA to be fully defined. offers a powerful probe of the solar chro- – Loukitcheva et al. (2017a) made mosphere. At present, observations in Science subarrays detailed comparisons of ALMA obser- Band 3 and Band 6 are supported. The The spectrum of continuum radiation vations of a sunspot at 1.25 and 3 mm intention of the Solar Development Team from the Sun is a key observable. Given with models of sunspot umbrae and is to provide support for observations in the dynamic nature of solar emissions at penumbrae, finding that none of the Band 7 (0.85 mm) and Band 9 (0.45 mm) millimetre and submillimetre wavelengths, extant models gives a satisfactory fit in Cycle 7 to allow deeper layers of the observations are needed in as many fre- to the dual-band high-resolution ALMA chromosphere to be observed. Evalua- quency bands as possible on a timescale observations. Observations between tion of Bands 7 and 9 for solar observing commensurate with the phenomenon 1.25 and 3 mm (Bands 4 and 5) is currently under way. In future years, of interest. In practice, this is a challenge. are needed, as well as additional multi- observations in frequency bands filling It may be possible to timeshare between band observations of many more the gaps between Bands 3, 6, 7, and 9 two or more frequency bands on times- sunspots. will be enabled. cales of tens of seconds for some pro- grammes, but others (for example, obser- – Allisandrakis et al. (2017) exploited fast- Polarimetry vations of solar flares) will require strictly scan total power maps at both 1.25 A key capability of ALMA for all scientific simultaneous observations in two or and 3 mm to assess the brightness communities is to fully support the quan- more frequency bands. This will require variation of the quiet Sun from the cen- titative characterisation of the polarisation dividing the array into two or more sub­ tre to the limb, inverting the transfer properties of the observed millimetre/ arrays that are each capable of observing equation to infer the dependence of submillimetre radiation, usually in the the Sun independently. plasma temperature on optical depth. form of the Stokes polarisation parame- ters. Of fundamental importance to under- Fast regional mapping – Brajša et al. (2018) also used fast-scan standing a range of physical processes Solar-mode observing currently includes total power maps to characterise the is the measurement of chromospheric support of full disc total power mapping

The Messenger 171 – March 2018 29 Astronomical Science Bastian T. S. et al., Exploring the Sun with ALMA

as an adjunct to the interferometric ob­­ American contribution) and ESO (for the European Loukitcheva, M. et al. 2017a, A&A, 601, A43 servations. The total power maps have contribution). The help and cooperation of engi- Phillips, N. et al. 2015, Revolution in Astronomy with neers, telescope operators, astronomers-on-duty, ALMA: The 3rd Year, 499, 347 scientific value in their own right and, for the Extension and Optimisation of Capabilities (EOC) Shimojo, M. et al. 2017a, Sol. Phys., 292, 87 certain applications, may be preferable — formerly the Commissioning and Science Verifica- Shimojo, M. et al. 2017b, ApJ, 841, L5 to interferometic observations. The ALMA tion) team, and staff at the ALMA Operations Sup- Wedemeyer, S. et al. 2015, Advances in Space Solar Development Team has demon- port Facility were crucial for the success of solar Research, 56, 2679 commissioning campaigns in 2014 and 2015. We are Wedemeyer, S. 2016, The Messenger, 163, 15 strated that fast-scan mapping could be grateful to the ALMA project for making solar obser- Wedemeyer, S. et al. 2016, SSRv, 200, 1 performed on sub-regions of the Sun at a vations in the millimetre and submillimetre possible. White, S. M. et al. 2017, Sol. Phys., 292, 88 relatively high cadence (tens of seconds). Yagoubov, P. A. 2013, 38th International Continuous fast-scan mapping of regions Conference on Infrared, Millimeter, and Terahertz References Waves (IRMMW-THz), 1, DOI: 10.1109/IRMMW- on scales of just a few arcminutes using THz.2013.6665775 two or more total power antennas to pro- Alissandrakis, C. E. et al. 2017, A&A, 605, A78 vide multi-band imaging would be a valu- Bastian, T. S. et al. 2017, ApJ, 845, L19 able mode to observe certain aspects of Brajša, R. et al. 2018, A&A, accepted Links De Pontieu, B. et al. 2014, Sol. Phys., 289, 2733 solar flares and eruptive phenomena. Clark, T. A., Naylor, D. A. & Davis, G. R. 2000a, 1 The ALMA solar ephemeris generator: http://celes- A&A, 357, 757 tialscenes.com/alma/coords/CoordTool.html Clark, T. A., Naylor, D. A. & Davis, G. R. 2000b, 2 JPL Horizons web interface: https://ssd.jpl.nasa. Acknowledgements A&A, 361, 60 gov/horizons.cgi Heinzel, P. et al. 2015, Sol. Phys., 290, 1981 3 ALMA solar observations: http://www.almaobser- The ALMA solar commissioning effort was sup- Iwai, K. et al. 2017, ApJ, 841, L20 vatory.org/en/announcement/alma-starts-observ- ported by ALMA development grants from the Kaufmann, P. et al. 2004, ApJ, 603, 121 ing-the-sun/ National Astronomical Observatory of Japan (NAOJ; Kosugi, T. et al. 2007, Sol. Phys., 243, 3 4 ALMA science verification data:https://almasci - for the East Asia contribution), the National Radio Krucker, S. et al. 2013, A&ARv, 21, 58 ence.nrao.edu/alma-data/science-verification Astronomy Observatory (NRAO; for the North Loukitcheva, M. et al. 2017b, ApJ, 850, 35 D. Kordan/ESO D.

ALMA in 2017, just after a particularly harsh winter.

30 The Messenger 171 – March 2018 Astronomical Science DOI: 10.18727/0722-6691/5066

The ESO Diffuse Interstellar Band Large Exploration ­Survey (EDIBLES)

Jan Cami1, 2 11 Department of Physics, The Catholic interstellar “mystery molecules”, and turn Nick L. J. Cox 3, 4 University of America, Washington DC, DIBs into powerful diagnostics of their Amin Farhang1, 5 USA environments in our Milky Way Galaxy Jonathan Smoker 6 12 Instituut voor Sterrenkunde, KU Leuven, and beyond. We present some prelimi- Meriem Elyajouri 7 Belgium nary results showing the unique capa- Rosine Lallement 7 13 George Washington University, bilities of the EDIBLES programme. Xavier Bacalla 8 ­Washington DC, USA Neil H. Bhatt1 14 UK Astronomy Technology Centre, Emeric Bron 9 Royal Observatory Edinburgh, UK The diffuse interstellar bands Martin A. Cordiner10, 11 15 ESTEC, ESA, Noordwijk, The Alex de Koter 3, 12 Netherlands One of the longest-standing problems in Pascale Ehrenfreund13 16 Université de Toulouse, UPS-OMP, modern astronomical spectroscopy is Chris Evans14 IRAP, Toulouse, France associated with the identification of the Bernard H. Foing15 17 CNRS, IRAP, Toulouse, France chemical species that produce the dif- Atefeh Javadi5 18 Sorbonne Université, Observatoire de fuse interstellar bands (DIBs; see Cami Christine Joblin16, 17 Paris, Université PSL, CNRS, LERMA, & Cox, 2012 for a recent review) — a Lex Kaper 3 Meudon, France problem that first surfaced almost a cen- Habib G. Khosroshahi 5 19 School of Chemistry, University of tury ago. The DIBs are a collection of Mike Laverick12 ­Nottingham, UK over 400 absorption features that appear Franck Le Petit18 20 Instituto de Astrofísica de Canarias in the spectra of reddened stars. Their Harold Linnartz 8 (IAC), La Laguna, Tenerife, Spain interstellar nature is clear, but their origin Charlotte C. M. Marshall19 21 Universidad de La Laguna, Tenerife, is unknown (although a few DIBs in the Ana Monreal-Ibero 20, 21 Spain near-infrared part of the spectrum are 22 22 + Giacomo Mulas INAF–Osservatorio Astronomico di attributed to C60; see below). Given their Evelyne Roueff18 Cagliari, Selargius, Italy strength and their widespread occur- Pierre Royer12 23 NASA Ames Research Center, Space rence in harsh interstellar environments, Farid Salama 23 Science & Astrobiology Division, the DIB carriers are most likely abundant, Peter J. Sarre19 ­Mountain View, USA stable, carbonaceous species such as Keith T. Smith 24 24 AAAS Science International, carbon chains, polycyclic aromatic hydro- Marco Spaans 25 ­Cambridge, UK carbons (PAHs), fullerenes or closely Jacco T. van Loon 26 25 Kapteyn Institute, University of related species. Despite their unknown Gregg Wade 27 ­Groningen, The Netherlands identity, the DIBs are being used increas- 26 Lennard-Jones Laboratories, Keele ingly often as tools, for example to map University, UK the interstellar medium in 3D (Bailey et al., 1 Department of Physics and Astronomy 27 Department of Physics, Royal Military 2016). The eventual identification of DIB and Centre for Planetary Science and College of Canada, Kingston, Canada carrier(s) will make DIBs very powerful Exploration (CPSX), The University of diagnostics in the interstellar medium. Western Ontario, London, Canada 2 SETI Institute, Mountain View, USA The ESO Diffuse Interstellar Band Large The definite identification of DIB carriers 3 Anton Pannekoek Institute for Astron- Exploration Survey (EDIBLES) is a Large must come from an accurate match omy, University of Amsterdam, The Programme that is collecting high-signal- between the observed spectroscopic Netherlands to-noise (S/N) spectra with UVES of a features in a low-temperature gas-phase 4 ACRI-ST, Sophia Antipolis, France large sample of O and B-type stars cov- laboratory experiment and the DIBs seen 5 School of Astronomy, Institute for ering a large spectral range. The goal in astronomical observations. Indeed, Research in Fundamental Sciences, of the programme is to extract a unique laboratory data not only provide accurate Tehran, Iran sample of high-quality interstellar spec- rest wavelengths and bandwidths (includ- 6 ESO tra from these data, representing differ- ing transitions beyond the origin band) of 7 GEPI, Observatoire de Paris, PSL ent physical and chemical environments, possible carriers, but the controlled con- Research University, CNRS, Université and to characterise these environments ditions in the laboratory also allow the Paris-Diderot, Sorbonne Paris Cité, in great detail. An important component derivation of oscillator strengths that are Meudon, France of interstellar spectra is the diffuse inter- needed to estimate column densities. 8 Sackler Laboratory for Astrophysics, stellar bands (DIBs), a set of hundreds However, the sheer number of possible Leiden Observatory, Leiden University, of unidentified interstellar absorption DIB carrier candidates to measure exper- The Netherlands lines. With the detailed line-of-sight imentally is so challenging — for exam- 9 ICCM, Madrid, Spain information and the high-quality spectra, ple, there are more than 1.2 million PAH 10 Astrochemistry Laboratory, NASA EDIBLES will derive strong constraints species with 100 or fewer C atoms — ­Goddard Space Flight Center, on the potential DIB carrier molecules. that targeted astronomical observations ­Greenbelt, USA EDIBLES will thus guide the laboratory are needed to guide the selection of the experiments necessary to identify these most promising candidates by providing

The Messenger 171 – March 2018 31 Astronomical Science Cami J. et al., EDIBLES

564 nm RedU HD 79186, 80 Flats S/N = 1400 1.02 1.02 EDIBLES S/N ~ 1000

x 1.00 1 flu

x flu

0.98 0.98 S/N ~ 555 Normalised 0.96 HD 79186, 5 Flats Normalised S/N = 880 0.96 ADP 0.94

0.94 6120 6125 6130 5794 5796 5798 5800 Wavelength (Å) Wavelength (Å) constraints on the carrier species. signal-to-noise ratio (median S/N ~ 500– Figure 1. Left: A comparison between the results High-resolution observations of DIB 1000 per target) over a large spectral of the ESO Archive Data Products (ADP) and the EDIBLES processing pipeline (bin size: 0.02 Å). line profiles can be used to estimate the range (3050–10420 Å), and with targets ­Figure from Cox et al. (2017), reproduced with per- size and geometry of the DIB carrier that represent very different physical mission from A&A. Right: The EDIBLES spectrum ­molecules as well as their excitation ­conditions along the lines of sight. DIB of HD 79186 around the 5797 Å DIB when using properties (see, for example, Marshall targets are typically bright, early-type (O- 80 flat fields (black) compared to the same obser­ vation using only five flat fields (red). et al., 2015). Correlation studies and and B-type) stars whose optical spectra investigations of how DIB strengths contain relatively few stellar lines. In these change in different environments yield spectra, the DIBs are more easily recog- A high S/N also requires a large number information about what drives variations nised and characterised. We selected of flat field exposures. We have devel- in the DIB properties, such as the ionisa- bright (V < 8 magnitudes) O- and B-type oped a custom data reduction procedure tion potential and chemical make up of stars, and constructed our sample so that to process flat field frames so that we can the DIB carriers (see, for example, Ensor we can probe a wide a range of inter­ attain the highest possible S/N (see et al., 2017). stellar environment parameters including Cox et al., 2017). Figure 1 illustrates how interstellar reddening E(B-V) ~ 0–2 mag- the addition of a large number of flat

While there has been steady progress nitudes, visual extinction AV ~ 0–4.5 mag- fields can greatly improve the quality of in the field over the years, most studies nitudes, total-to-selective extinction the resulting spectra. Using the same focus on the properties of a small num- ratio RV ~ 2–6, and a molecular hydrogen recipes and a higher number of flat field ber of DIBs, over particular wavelength fraction f(H2) range ~ 0.0–0.8. Our final frames — even when obtained on differ- ranges and in particular environments, target list contains 114 objects of which ent dates — can increase the S/N of or alternatively deal with large datasets 97 have been observed to date. Further other good-quality science observations and “average” properties of the DIBs details about the goals, objectives and in the UVES archive. In the red part of the (for example, Lan et al., 2015). Significant sample selection can be found in Cox spectrum, we could also improve and progress in the field can be expected et al. (2017). fine-tune the wavelength calibration using from a high-quality, sensitive survey of the large number of telluric lines available interstellar features (DIBs, but importantly EDIBLES is an approved Large Pro- in our high-resolution spectra. also known interstellar atoms and mole- gramme that started in September 2014 cules) over a large spectral range and (ESO period 94) under Programme ID EDIBLES is unique in its combination representing differing interstellar environ- 194.C-0883. The total allocated tele- of spectral resolution, wavelength cover- ments (Cami & Cox, 2014). The ESO scope time, excluding daytime calibra- age, sensitivity and sample size and this ­Diffuse Interstellar Band Large Explora- tions, is 284 hours. As a programme, promises great advances in the field. tion Survey (EDIBLES) is such a survey. EDIBLES has been optimised, in terms of As illustrated below, the high spectral selected targets and observing strategy, resolution allows us to study individual to obtain observations when weather DIB line profiles for a large number of EDIBLES conditions are typically too poor for regu- DIBs, yielding size estimates for their lar programmes (called “filler conditions”) ­carrier molecules when clear substruc- The aim of EDIBLES is to collect a large and thus helps to optimise the use of the tures are present. The high sensitivity sample of interstellar spectra with UVES telescope. This makes it a less efficient facilitates studying both strong and weak (Smoker et al., 2009) at high spectral process to reach a sufficiently high S/N, DIBs simultaneously. This is important ­resolution (R ~ 70 000 in the blue and and we therefore require a large number since laboratory spectra of typical DIB 100 000 in the red arm), with a very high of exposures. carriers often result in several transitions

32 The Messenger 171 – March 2018 of comparable strength in the optical Figure 2. Upper panel: range, in contrast with the fact that no ­Profiles of the 6614 Å DIB 1 towards HD 170740 (deeper, two DIBs have been found that undenia- blue trace) and HD 147165 bly originate from the same species (with (broader, red trace). The + spectra are normalised to a the possible exception of the C60 DIBs). We expect that EDIBLES will reveal the 0.96 common integrated inten- sity and the ordinate values first pair of perfectly correlating DIBs. are those for HD 170740. The spectra are shifted to The large spectral coverage combined 0.92 the interstellar restframe x using K I radial velocities.

with the high resolution — which allows flu Lower panel: The difference very good telluric corrections — will ve between the normalised explore wavelength ranges over which profiles of the DIB in few or even no sensitive DIB searches Relati 0.88 HD 170740 and HD 147165. have ever been carried out. Furthermore, this range includes a large number of known interstellar absorption lines — due −0.02 to atoms and small molecules such as

CN or C2 — which play an important role 0 in EDIBLES. They enable us to accurately define the physical conditions in a large 0.02 sample of lines of sight along which DIBs are measured, which is unprecedented 6612.0 6613.0 6614.0 6615.0 6616.0 on this scale. All these characteristics will Wavelength (air, Å) enormously constrain the number of pos- sible carrier molecules. interpreted as arising from a stronger hot ear molecule (Thorburn et al., 2003). Fur- band contribution (Marshall et al., 2015). ther constraints on the properties of the EDIBLES is also ideally suited for seren- carrier will come from detailed analyses dipitous studies that are not directly The details of the band profile depend of the line profile shape of the 2C -DIBs. related to the DIBs. The large number of on the rotational and vibrational tempera- Since many of the C2-DIBs are weak and observations of O and B stars will turn tures and EDIBLES is designed to make high spectral resolution is required to out to be very useful for studies of mas- progress in our understanding of pre- resolve the profiles, substructure in the sive stars and their stellar winds. Since cisely how these temperatures cause profiles of the 2C -DIBs was only reliably our survey also includes observations spectral changes. Indeed, the large num- established for three to four C2-DIBs, of the same lines of sight at different bers of EDIBLES sightlines sample the although asymmetries in observed pro- epochs, the survey can also be used and possible range of rotational and vibrational files suggested that more of the 2C -DIBs complemented by archival data, to study temperatures in interstellar clouds, and could exhibit substructure (Galazutdinov small-scale variations in interstellar lines information on these temperatures can et al., 2002). over time. be derived from other molecular absorp-

tion lines in the EDIBLES spectral range. In the EDIBLES dataset, we detect C2 A-X Resolved substructures in DIB line Modelling of these band profiles will thus rovibronic bands around 7700, 8800 and profiles provide the link between the observed 10 100 Å in 25 sightlines, representing The high-resolution, high-S/N spectra spectral variations and the changes in one of the largest samples to date for this of the EDIBLES survey reveal profile temperature; in turn, this will greatly con- important species (Cordiner et al., in ­substructures in a large number of DIBs, strain the properties (for example, size preparation). This is another demonstra- and subtle variations in these profiles and geometry) of the possible carrier tion of the unique, extremely high sensitiv- from one line of sight to another. A good molecules. ity of our EDIBLES survey for the detec- example is the well-known triplet struc- tion of weak spectral features. Excitation ture found in the 6614 Å DIB towards The C2-DIBs modelling of these C2 spectra permits HD 170740 and HD 147165 (σ Sco), shown A particularly intriguing subset of the new insights into the temperatures and in Figure 2. We compare the DIB profiles, DIBs are the so-called C2-DIBs (Thorburn densities of diffuse molecular gas. normalised to a common integrated et al., 2003); these are features that cor- intensity using an approach introduced relate especially well with the column From this sample, we selected several by Marshall et al. (2015). It is notable that density of C2 molecules along the line of EDIBLES targets that exhibit strong the absorption depths for the sub-peaks sight. This could imply that C2-DIB carri- C2 lines and that are “single clouds”, i.e., that are redwards and bluewards of the ers are chemically linked to C2. Moreover, there is only one dominant interstellar strongest central absorption differ for several C2-DIBs appear in pairs that are cloud along the direct line of sight to the the two sightlines, and that the redward separated by the same spacing of about target. For this sample of targets, we –1 tail is stronger and more extended for 20 cm , reminiscent of the spectroscopic find thatall C2-DIBs have resolved struc- HD 147165; this character­istic has been signature of spin-orbit interaction in a lin- ture in their profiles (Elyajouri et al., in

The Messenger 171 – March 2018 33 Astronomical Science Cami J. et al., EDIBLES

5418 Å 1.00 5512 Å 5769 Å 1.00 1.00 0.99 0.98 0.98 0.98 New 0.96 0.97 0.96

x 1.00 1.00 1.00 flu

0.99 0.98 0.99 Normalised

0.98 0.98 0.96

0.97 0.97

0.94 0.96 0.96 5417 5418 5419 5420 5421 5512 5513 5514 5768 5769 5770 Wavelength (Å) Wavelength (Å) Wavelength (Å)

Figure 3. A few examples of the C2-DIB profiles at son with interstellar spectra. The central uals) and a Gaussian fit to that depres- 5418.91, 5512.62 and 5769.08 Å. Coloured lines dis- wavelengths of the two strongest bands sion has an absorption depth that agrees play the individual sightlines. The black profile on top is the average normalised profile obtained by stack- in the laboratory experiments agree with with predictions, given the strength of the + ing the deepest bands of three single cloud targets. the central wavelengths of the two DIBs, other C60 bands. While this does not yet within uncertainties of ~ 0.1 Å. The labo- prove beyond any doubt that the 9428 Å ratory spectrum furthermore exhibits DIB is present, the EDIBLES data support + preparation; Figure 3). The high resolution three weaker bands and several authors the identification of these DIBs with C60 and S/N allow us to conclude with con­ have found evidence for these bands as (Lallement et al., 2018). fidence that these substructures are nei- well (for example, Walker et al., 2017; ther telluric nor stellar in origin, and that Cordiner et al., 2017). The high spectral resolution of the the single-cloud nature of the targets ­EDIBLES data furthermore allows the + eliminates multi-cloud confusion as well. Unequivocally confirming even the pres- study of some of the C60 DIBs profiles These substructures are thus intrinsic to ence of these weaker bands, however, is despite the telluric contamination. For the C2-DIBs and will reveal a lot about greatly complicated by the many strong example, in the lower panel of Figure 4 the properties of their carrier molecule(s). telluric spectral features in the wavelength we show how co-adding 79 individual + range over which the C60 bands occur observations of 43 different targets reveals + The DIBs attributed to C60 (Figure 4, top). Typically, the analysis is the first evidence for an enormous amount Foing & Ehrenfreund (1994) used labora- performed on a corrected spectrum, cre- of detail in the substructure of the strong + tory measurements to predict that inter- ated by dividing out the telluric lines by 9577 Å C60 DIB. This is possible because + stellar, gas-phase C60 molecules would means of a transmission model or the this DIB is only partially affected by telluric exhibit transitions near 9577 Å and spectrum of a telluric standard star. How- lines; the different interstellar cloud radial 9632 Å. A dedicated search did indeed ever, with such strong telluric lines — also velocities then cause different parts of result in the discovery of two DIBs near variable on short timescales — residuals the band to appear in the “telluric-free” those wavelengths with band characteris- are unavoidable and can result in severe window (Lallement et al., in preparation). tics that were expected for this species. artefacts. Figure 4 (middle) shows that, Small-scale variations in these substruc- However, the laboratory data that they even when dividing out a spectrum with a tures from one line of sight to another used were obtained in cryogenic matri- very similar telluric profile (in this case of can then be used to study the fullerene ces in which the band positions and pro- HD 54662), such residuals occur. molecular physics and the impact of the files may be affected. Obtaining a gas- local physical conditions. phase spectrum at low temperatures In the corrected spectrum, a clear feature has proven to be very challenging, but shows up at 9412 Å; this is a known DIB OH+ and the cosmic ray ionisation rate + Campbell et al. (2015) succeeded in that is unrelated to C60. At the same time, When Bhatt & Cami (2015) performed developing a technique to reliably meas- at the expected position of the 9428 Å a sensitive survey of interstellar lines + ure the electronic spectrum under con­ C60 band, there appears to be a depres- in the near-ultraviolet by stacking 185 ditions that are appropriate for compari- sion (somewhat masked by telluric resid- UVES archival observations of reddened

34 The Messenger 171 – March 2018 Figure 4. Upper: HD 169454 HD 54662 a time series since 1995 of the He I line The ­EDIBLES spectra of 2200 profile at 5876 Å in HD 148937, a mag- HD 169454 and HD 54662 in the range netic Of?p star that is at the centre of the 2000 of two weak DIBs: the bipolar emission nebula NGC 6164. This

x 9412 Å DIB (unrelated object has been monitored for a long Flu to C+ ) and a weak DIB 1800 60 time, and small variations in stellar line at 9428 Å which is due + profiles have been attributed to rotational to C60 (adapted from 1600 Lallement et al., 2018). modulation (Nazé et al., 2008). We noticed Middle: The HD 169454 9410 9420 9430 9440 9450 that the EDIBLES observations that were spectrum divided by carried out in 2015 revealed a very differ- the one of HD 54662. DIB ent line profile compared to all previously 9428 Å Lower: A com­posite 1.5 showing partially published profiles (c.f. Figure 14 in Cox resolved substructure et al., 2017). Many more stellar lines show in the strong 9577 Å 1.4 + clear variations in their shapes and their C60 DIB. All fluxes are in x arbitrary units. wavelengths. A careful analysis reveals

Flu that this object is a massive spectroscopic 1.3 DIB 9412 Å binary, with a preliminary period of at least 18 years. The ­EDIBLES observations 1.2 just happened to be acquired close to periastron passage, where effects on the 1.1 9410 9420 9430 9440 9450 spectrum would be most pronounced Wavelength (Å) (Wade et al., in preparation).

Outlook 1.00 With EDIBLES, we have currently ob­­

N served 97 early-type stars at high spectral umb resolution and at high S/N over a large

0.99 er

70 spectral range. The first studies, some of of of

x

cont which we have presented here, clearly Flu show the enormous potential for new dis- 60 ribu 0.98 coveries with this dataset. To ensure opti- ting ex ting mal exploitation and interpretation of this unique data set, the EDIBLES team is

50 posu composed of researchers from a diverse 0.97

re community, including observational s 40 astronomers as well as experts in molecu- lar astrophysics, interstellar physics and 9572 9574 9576 9578 9580 9582 9584 Wavelength (Å) chemistry, and laboratory astrophysics. In addition to the scientific analyses, we have targets, they discovered five new narrow The high S/N in the EDIBLES data and tested and demonstrated a recipe that is inter­stellar features in the stacked spec- the wavelength coverage in the near-­ available to the community, which can trum that were too weak to be discerned ultraviolet now show these very weak significantly increase the S/N of UVES in a single observation. Zhao et al. (2015) features almost routinely, and enable the observations. The EDIBLES team is fur- confirmed two of these features and calculation of the cosmic ray ionisation thermore committed to pro­viding the com- identified them with transitions due to rate for a much larger sample than before, munity with a catalogue detailing a large OH+; they also found several more OH+ thus expanding the available line-of-sight number of interstellar quantities for these lines in addition to the already well known information potentially also relevant for sightlines — including DIB measure- line at 3583.76 Å. With several lines the DIBs analysis (Bacalla et al., in prepa- ments. This catalogue is likely to serve as ­available that all arise from the ground ration; Figure 5). Indeed, the detection the DIB benchmark reference for many state level, it is possible to accurately and analysis of such diagnostic molecules years to come. While the EDIBLES team derive the corresponding­ population and allow the community to interpret the DIB focuses on the interstellar studies, the infer the cosmic ionisation rate in diffuse measurements within the context of their same data will also be fruitful ground for a inter­stellar clouds, something which physical surroundings. diverse range of other projects, including has only been possible using space tele- stellar spectroscopy analyses. It is clear scopes, and which yields comparable Variability in HD 148937 that ­EDIBLES will leave a significant legacy results. As an example of the potential for seren- to the astronomical community at large. dipitous discoveries, we show in Figure 6

The Messenger 171 – March 2018 35 Astronomical Science Cami J. et al., EDIBLES

635 HD 148937 630

625 x 1995

Flu 620

615

610 2002

1.000 2006 0.995 x flu

flux

0.990

0.985 2007 0.980 Normalised

Normalised 0.975 0.970 2008 0.965 3σ 0.0025 0.0000 2009 –0.0025 –3σ 3582.753583.25 3583.753584.25 3584.75 Wavelength (Å) 2010 Acknowledgements Figure 5 (above). The strongest OH+ line at 3584 Å in the EDIBLES Jan Cami and Amin Farhang acknowledge support spectrum of HD 80558, with a from a Natural Sciences and Engineering Research Voigt profile­ fit. 5860 5880 5900 Council (NSERC) Discovery Grant and a Science and Wavelength (Å) Engineering Research Board (SERB) Accelerator Award from Western University. Meriem Elyajouri acknowledges funding from the Region Île-de- HD 148937 France through the DIM-ACAV project. Peter J. Sarre thanks the Leverhulme Trust for award of a Lever- hulme Emeritus Fellowship. Charlotte C. M. Marshall thanks EPSRC and the University of Nottingham for financial support. OWN archive 26 May 2010

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Cami, J. & Cox, N. L. J., eds. 2014, IAU Symposium, OWN archive 05 Jun 2014 Vol. 297, The Diffuse Interstellar Bands Campbell, E. K. et al. 2015, Nature, 523, 322 Cordiner, M. A. et al. 2017, ApJl, 843, L2

Cox, N. L. J. et al. 2017, A&A, 606, A76 Normalised Ensor, T. et al. 2017, ApJ, 836, 162 EDIBLES Discovery 15 Sep 2015 Foing, B. H. & Ehrenfreund, P. 1994, Nature, 369, 296 Galazutdinov, G. et al. 2002, A&A, 396, 987 Figure 6. Upper Right: Archival Lallement, R. et al. 2018, arxiv:1802.00369 observations showing the line pro- Lan, T.-W., Ménard, B. & Zhu, G. 2015, MNRAS, files of the He I line at 5876 Å in 452, 3629 EDIBLES Follow-up 23 Apr 2017 HD 148937 between 1995 and Marshall, C. C. M., Krełowski, J. & Sarre, P. J. 2015, 2010. Right: Archive observations MNRAS, 453, 3912 from the Southern Galactic O- and Nazé, Y. et al. 2008, AJ, 135, 1946 WN-type stars (OWN) campaign Smoker, J. et al. 2009, The Messenger, 138, 8 (Barba et al., 2010) and EDIBLES Thorburn, J. A. et al. 2003, ApJ, 584, 339 OWN Follow-up 15 Aug 2017 observations of the same line Walker, G. A. H. et al. 2017, ApJ, 843, 56 between 2010 and 2017. Note how Zhao, D. et al. 2015, ApJl, 805, L12 the character of the line profile changed markedly in 2014–2015 (Figure from Wade et al., in prepa- 5860 5880 5900 ration). Wavelength (Å)

36 The Messenger 171 – March 2018 Astronomical Science DOI: 10.18727/0722-6691/5067

APEX Band 9 Reveals Vibrationally Excited Water Sources in Evolved Stars

1 Figure 1. Vibrational Alain Baudry E (cm–1) Fabrice Herpin1 energy diagram of water 2 showing all states up Elizabeth Humphreys to about 4000 cm–1. Karl Torstensson 2 The states are ordered Wouter Vlemmings 3 along the horizontal axis Anita Richards 4 according to the second 4000 4 (001) vibrational state v2. We Malcolm Gray show the two main vibra- Carlos De Breuck 2 tional transitions from 3 (100) (020) Michael Olberg the ground-state (v1 = 0, v2 = 0, v3 = 0) to (010) and to (001) around 6.27 and 2.66 µm. The 1 Laboratoire d’astrophysique de infrared transitions µm ­Bordeaux, Université de Bordeaux, 2000 ­correspond to symmet-

France 66 (010) ric bending and 2 2. anti-symmetric stretch- ESO ing of the water mole- 3 Onsala Space Observatory, Department cule. The 658 GHz rota- of Space, Earth and Environment, µm tional transition­ lies in 27 ­Chalmers University of Technology, 6. the (010) state. Sweden 4 0 Jodrell Bank Centre for Astrophysics, (000) University of Manchester, UK v = 0 2 v2 = 1 v2 = 2

wards – compete with gravity during the 22 GHz line emission is often peculiar: We have used the Atacama Pathfinder late stages of stellar evolution to shape the spectral features can be very narrow, Experiment (APEX) telescope with the circumstellar envelopes. Magnetic fields polarised and time variable. In addition, sensitive Swedish-ESO PI APEX (SEPIA) or nearby companions may also play a Very Long Baseline Interfer­ometry (VLBI) Band 9 receiver to discover several role in this shaping process. Owing to observations demonstrate that line new vibrationally excited line sources the presence of shocks and stellar winds, brightness temperatures may reach of water at 658 GHz in the atmosphere complex chemistry is observed in the about 1012 K in some RSGs. Such a high, of selected O-rich evolved stars. We extended atmospheres and the circum- non-thermal temperature is typical of have shown that this transition is mas- stellar envelopes of AGBs or RSGs (for maser action. Maser emission from vari- ing and can be used to probe the gas in example, Justtanont et al., 2012; Alcolea ous rotational levels above 640 K of the the dust formation zone or the wind et al., 2013). 22 GHz transition was also detected with beyond the central star. The 658 GHz various radio telescopes toward several line is widespread in evolved stars but Among all of the molecules that have been evolved stars. most sources are weaker than about identified towards evolved stars, water 300–500 Jy. However, some exceptional plays a prominent role because multiple Most of these rotational lines of water cases reach up to a few thousand Jy. infrared and radio wavelength transitions can be explained by collisional pumping New models incorporating several can be used to probe the physical con­ or by a combination of collisional and vibrationally excited transitions of water ditions and kinematics in these stars. A radiative pumping models. Recently, Gray allow us to predict the physical condi- first demonstration of the presence of et al. (2016) included energy levels up tions prevailing in 658 GHz sources. The water in the atmosphere of O-rich evolved to the (020) vibrational state lying some strongest ones could be mapped with stars was provided by the low-dispersion 4500 K (about 3150 cm–1 or 3.17 µm) ALMA to study the small-scale clumpi- identification of vibrational transition above the ground vibrational state (Fig- ness of the gas in the dust formation bands in the 1–3 µm domain (for exam- ure 1). Because of the large near-infrared zone or, more generally, the stellar wind. ple, Spinrad & Newburn, 1965). To probe flux density in evolved stars, rotational the layers of stellar atmospheres more transitions in the populated (010) and precisely one needs to observe pure (020) vibrational states should be detect-

Water: a masing molecule and rotational transitions of H2O in the radio able and can be used to probe the physi- ­ubiquitous tracer of stellar evolution domain with heterodyne receivers. cal conditions and dynamics of specific regions around stellar sources more Evolved objects such as asymptotic giant Strong 22 GHz emission from the ­thoroughly. Several rotational transitions branch (AGB) and red supergiant (RSG) J = 616–523 rotational transition of ortho-­ of H2O in the (010) state have been stars undergo strong mass loss (10–6 to water in the (000) ground vibrational state observed in the radio domain (see Table 1 –4 –1 10 M⊙ yr ) before they reach the white was first reported by Cheung et al. (1969) in Gray et al., 2016). However, these lines dwarf or supernova stage. Several mech- toward Orion. Since then, 22 GHz emis- tend to be weak, with the exception of anisms –0 for example shocks which can sion has been observed in hundreds of the transition discussed here; the J = 110– levitate stellar material, or radiation pres- young star-forming regions and evolved 101 rotational transition of ortho-water sure on dust which drags the gas out- stars (for example, Kim et al., 2014). The at 658 GHz lies in the (010) state about

The Messenger 171 – March 2018 37 Astronomical Science Baudry A. et al., APEX Band 9 Reveals Vibrationally Excited Water Sources in Evolved Stars

Source name Variabilty Reference Source name Variability Reference Table 1. A complete list of stars detected in the vibrationally excited line of ortho-water at 658 GHz WX Psc OH/IR 5 S Vir Mira 1 (as of September 2017). Stellar sources are ordered R Aql Mira 4 W Hya Mira 3, 2, 1, 5 by right ascension with two weak detections added at the end. Mira, RSG and SR stand for Mira-type, o Ceti Mira 5,2 RU Hya Mira 2 red supergiant and semi-regular variability respec- tively. OH/IR variability means the O-rich AGB star R Cet Mira 1 RX Boo SR 3 has an unknown or uncertain period of variability. R Hor Mira 2 S CrB Mira 3 References are: 1 This work; 2 Baudry et al. (2018); 3 Menten and Young (1995); 4 Hunter et al. (2007); RT Eri Mira 2 V351 Nor LP variable 1 5 Justtanont et al. (2012); 6 Bujarrabal et al. (2012); IK Tau Mira 4, 5, 2 IRAS 15568-4513 IR source 1 7 Teyssier et al. (2012); 8 Alcolea et al. (2013); 9 Richards et al. (2014). U Men SR 1 U Her Mira 3

R Dor SR 5, 1 V446 Oph SR 1 flux density limit of ~ 50 Jy. SiO emission R Cae Mira 1 V1006 Sco SR 1 is important because it is present in IRAS 05052-8420 AGB 1 AH Sco RSG 2 many O-rich evolved stars, and SiO and 658 GHz H O excitation levels are close TX Cam Mira 4, 5 RW Sco Mira 1 2 to each other (~ 1800 and 2360 K, respec- T Lep Mira 1 V1019 Sco SR 1 tively). A large fraction of our selected U Dor Mira 1 V4201 Sgr SR 1 sources comes from a homogeneous S Pic Mira 1 VX Sgr RSG 3 sample that was simultaneously observed in SiO and H2O (22 GHz) by Kim et al. R Oct Mira 1 RAFGL 5552 RSG? 1 (2010). Additional sources were added U Ori Mira 4 R Aql Mira 4 from the published literature using the L2 Pup SR 1 V342 Sgr Mira 1 same selection criteria in order to improve the coverage in declination. V578 Pup Mira 1 GY Aql SR 1 VY CMa RSG 3, 2, 4, 8, 9 V2234 Sgr AGB 1 We used the APEX telescope, using OH231.8+4.2 PPNebula 6 X Pav SR 2 the dual-sideband and dual-polarisation Band 9 Swedish-ESO PI receiver for KK Car Mira 1 T Mic SR 1 APEX (SEPIA; Belitsky et al., 2017). The RW Vel Mira 1 NML Cyg RSG 3, 7 receiver was tuned to place the 658 GHz RS Vel Mira 1 IRAS 20541-6549 AGB 1 water line and the J = 6–5 line of 13CO IW Hya Mira 1 R Peg Mira 1 at 661 GHz in the lower sideband where the atmospheric transparency is better. R Leo Mira 3, 4 R Aqr Mira 1 APEX is the only telescope other IRAS 10323-4611 C star 1 R Cas Mira 4, 5 than ALMA that is currently equipped to R Crt SR 3 observe at 658 GHz. RT Vir SR 3, 2 OH26.5+06 AGB 5 In our first observing campaign (from R Hya Mira 4, 2 RAFGL 5379 AGB 5 April to June 2016) we used SEPIA Sci- ence Verification time to observe nine 1640 cm–1 or 2360 K above the ground- emission was also detected with HIFI AGB stars and one supergiant source. level, and was first detected in variable from two AGB stars (Justtanont et al., All ten sources were detected, half of stars and two RSGs (Menten & Young, 2012) and from one protoplanetary which were new discoveries (Baudry et 1995). ­nebula (Bujarrabal et al., 2012). These al., 2018). In a second observing cam- observations suggested that 658 GHz paign (from July to September 2017), stellar sources are widespread. Along 39 other sources from our sample of late- Widespread 658 GHz line emission with our models, which predict that the type stars were observed with the fully toward evolved stars 658 GHz line can be strongly masing, commissioned SEPIA receiver. Both runs this suggests that the Atacama Large had good observing conditions with pre- Several years after the discovery by ­Millimeter/submillimeter Array (ALMA) cipitable water vapour below 0.7 mm. Menten and Young (1995), observations could map the most interesting sources. A total of 31 new 658 GHz sources were using the Submillimeter Array (SMA) detected (most of them are shown in Fig- and Herschel Space Observatory with With this in mind, we built a small cata- ure 2). Our 2016 and 2017 results more the Heterodyne Instrument for the logue consisting of nearly 100 candidate than double the number of stars known Far-Infrared (HIFI) expanded the number and known 658 GHz southern sources. to exhibit 658 GHz emission, demonstrat- of sources detected at 658 GHz to The sample is based on stars with ing that this water transition is widely

19 evolved, variable stars (Hunter et al., known H2O (22 GHz) and SiO (43 and/or excited in evolved O-rich stars. All our 2007; Justtanont et al., 2012). Weak 86 GHz) maser emission above a fixed data were reduced using the Continuum

38 The Messenger 171 – March 2018 2 2 0.4 GY AqlR1 Aqr TMic U Men 1 0.2 0.5 1 –28–24 –20–16 –12 0 0 0 0 –0.2 20 40 60 –40 –20 0 0 20 40 0 20 40 1.5 1 R CaeKK Car V351 NorR Peg 0.5 0.5 1 0.5 0 0 10 20 30 40 0 0 –1 –0.5 –0.5 –20–0–20 40 20 0 –100 –80–60 02040 0.4 30 R CetR Dor 3 L2 PupR1 AFGL5552 0.2 20 2 0.5 20 30 40 50 0 10 1 0 –0.2 0 ) –0.5

) 0

20 40 60 –20 0 20 (K

(K 20 40 60 0 20 40 * A * 3 A T

T 1.5 1 U Dor IW Hya 0.4 2 1 RW ScoV342 Sgr 0.5 0.2 1 0.5 28 32 36 40 44 0 0 0 0 –0.5 –0.5 –0.2 20 40 60 20 40 60 –100 –80 –60 –40 20 40 60 1.5 20 W HyaIRAS 10323 RS VelRW Vel 15 0.5 0.5 1 10 1 0.5 5 0 0 0 0 –0.5 20 40 60 0 20 40 60 –40 –20 0 20 –40 –20 0 20 –1 1 1 VLSR (km ) IRAS 20541T1 Lep S Vir 0.5 0.5 0.5 Figure 2. 658 GHz line 0 spectra of ortho-water 0 0 obtained by averaging –0.5 –0.5 both polarisations and –20–0–20 40 20 0 –20 02040 binning to 0.14 km s–1 V (km–1) V (km–1) V (km–1) LSR LSR LSR spectral resolution towards O-rich stars observed with APEX in 2017; one of the stars and Line Analysis Single-dish Software IRAS10323-4611 is (CLASS) software package1. C-rich. 28 The 658 GHz line profiles are smooth and centred close to the stellar velocity. 24 2016 & 2017 APEX Band 9 observations However, the strongest sources can exhibit asymmetrical line profiles and are 20 likely due to maser emission as explained below. The line widths at half intensity t are a few km s–1, with the exception of oun 16 –1 c the supergiant VY CMa (~ 11 km s ) and ce –1 the peculiar AGB L2 Pup (~ 14 km s ). our 12 The observed peak line intensities in s ­Figure 2 are given in terms of the antenna temperature, T *, and corrected for ab­­ Binned 8 Figure 3. Histogram A showing the 658 GHz sorption due to the Earth’s atmosphere, line flux density of which allows them to be converted into 4 ortho-water for all source flux densities. Observations sources observed with APEX in 2016 and 2017. show variations in TA* from 0.3–0.4 K for 0 The first bin from the weakest sources, up to about 31.8 K <<0>> 300600 9001200150018002100 > 2400 <<0>>–150 Jy starts at for R Dor. We derive a flux density to H2O 658 GHz line flux density (Jy) the 3-s level, at ~ 29 Jy.

The Messenger 171 – March 2018 39 Astronomical Science Baudry A. et al., APEX Band 9 Reveals Vibrationally Excited Water Sources in Evolved Stars

22 GHz658 GHz Figure 4. Maser negative optical depth contours for the 22 and 658 GHz lines in the kinetic temperature 2800.0 versus H2 density plane according to Gray et al. (2016) modelling. Contours are equally spaced up to 5.0 0 .0 the maximum value of 12.

1 2300.0 0.0

5.0 VY CMa (Richards et al., 2004) showed that the broad aggregate line profile )

.0 0

0 0 (K 1800.0 5. is made up of several­ spatially and spec- 5.0 1 0. e 10

.0 trally distinct gas clumps. The narrower spectral features are distributed within 1300.0 50–250 milli­arcseconds of the central mperatur

Te star in a region where SiO masers are

0.0 800.0 1 also present. 5.0 0.0 5.0 It is possible to prove indirectly that the 300.0 658 GHz emission is excited close to the 8.09.0 10.0 8.09.0 10.0 star by comparing the 658 GHz velocity n(H ) (cm–3) n(H ) (cm–3) 2 2 extent at “zero” intensity with the same quantity for the SiO maser emission at antenna temperature conversion factor of In the unique case of VY CMa Richards et 86 GHz in the first vibrational state for a 120 (± 10) Jy K–1 from 2017 (unresolved) al. (2014) were able to map the 658 GHz small sub-sample (Baudry et al., 2018). ­Uranus observations. The observed emission with ALMA and identify gas This can be justified because: a) the SiO source flux density varies from ~ 40– “clumps” with brightness temperatures v = 1 state energy is around 1800 K and 3800 Jy, a broad range which partially above 0.3–4 × 107 K. The nearly contem- close to the (010) vibrational state of the reflects different distances to the sources, poraneous 22 and 658 GHz observations 658 GHz line; b) the emission peak veloc- and is partially due to different maser of Menten and Young (1995) can be used ities of both maser lines are close to each line amplification processes or stellar to constrain Tb(658) in other evolved other; and c) VLBI observations indicate activity. Nearly all sources are weaker stars. Assuming that both emissions at a that SiO masers are formed within ~ 5 R* than 300–500 Jy. Figure 3 shows the his- given spectral velocity are excited in of the central object. The loose correlation togram of 658 GHz flux density for all comparable gas volumes, we expect val- found (see Figure 5) suggests that both 4 10 of our sources, which has a peak below ues of Tb(658) ~ 10 –10 K from 22 GHz masers are excited in similar environments 150 Jy. Table 1 lists the variability charac- observations of AGBs. This clearly indi- close to the central star, but this should teristics of all evolved stars for which cates suprathermal emission and maser be confirmed with a larger sample. there are 658 GHz water line detections action for VY CMa and AGBs. (as of September 2017). In a few stars, the 658 GHz line width to Finally, the multi-level, radiative transfer ‘zero’ intensity (defined as the width calculations applied to physical condi- down to 2- to 3-s spectral noise) is com- On the masing nature of the 658 GHz tions and material slabs typical for evolved parable to that measured for CO, which emission stars show that the 658 GHz line can be traces the circumstellar envelope expan- inverted and masing (Gray et al., 2016). In sion. In four stars — R Aqr, U Dor, L2 We do not think that the 658 GHz line Figure 4 we compare the physical condi- Pup and R Peg — the 658 GHz low-level is thermally broadened and excited for tions leading to 22 and 658 GHz maser emission is broader than the correspond- several reasons. First, the line width at emission. Negative 658 GHz opacities as ing CO velocity extent; see horizontal, half-intensity (which is broader than the high as 10 are reached for kinetic temper- red bar in Figure 2 for CO, J = 2–1 veloc- expected 2–2.5 km s–1 thermal line width) atures from 1000–2800 K or over and for ity extent from Groenewegen et al. (1999), remains small compared to the typical densites of ~ 1010 cm–3, suggesting layers ­Kerschbaum & Olofsson (1999) and 10 to 20 km/s line width of the 13CO, of material that are relatively close to the ­Winters et al. (2002). This low-intensity J = 6–5 line requiring hot gas conditions stellar photosphere. emission is unlikely to trace the envelope (compared to low-J CO emission). And, expansion in regions that are cooler than for most stars, the 658 GHz line width at Figure 4 also shows that the loci of required to excite the 658 GHz line. On half-intensity remains small compared to inverted 22 GHz line emission are broader the other hand, it could be related to gas the low-J CO line width. Secondly, since than those at 658 GHz. This is expected acceleration close to the central star and/ the flux density of the 658 GHz transition for a transition which is both collisionally or perhaps to shocks; this is also sup- can reach several thousand Jy we may and radiatively excited and thus easily ported by 658 GHz filaments observed infer that the line brightness temperature detected in a variety of physical environ- by ALMA in VY CMa. Even if the bulk of

Tb(658) is well above the gas kinetic tem- ments. Along with the high-­energy levels the 658 GHz emission is masing we can- perature (though our single dish observa- at 658 GHz, it appears likely that the not exclude the possibility that the low-­ tions only provide weak constraints). 658 GHz line is formed in layers close to intensity radiation is due to weak thermal the photosphere. The 658 GHz map of excitation of the gas.

40 The Messenger 171 – March 2018 Figure 5. Full width at 40 the Orion KL region (Hirota et al., 2016), VY CMa zero intensity (FWZI) at and could also be used for phase 658 GHz (vibrationally calibration. excited H2O) versus FWZI at 86 GHz (SiO, v = 1 maser) for 10 30

) sources (triangles) Acknowledgements –1

s observed in Baudry et

m al. (2018) and 10 addi- Our data were acquired with the APEX telescope (k

5 tional sources. The equipped with the Swedish-ESO Band 9 receiver. 68 R Hor and VY CMa APEX is a collaboration between the Max-Planck-In- ZI 20 labels mark the two stitut für Radioastronomie, ESO and the Onsala FW ends of the observed Space Observatory. We warmly thank the APEX staff loose correlation. who carried out the APEX SEPIA Band 9 observa- tions. 10

References R Hor Alcolea, J. et al. 2013, A&A, 559, 93 20 40 60 Baudry, A. et al. 2018, A&A, 609, 25 FWZI (km s–1) 86 Belitsky, V. et al. 2017, arXiv171207396B Bujarrabal, V. et al. 2012, A&A, 537, 8 Cheung, A. C. et al. 1969, Nature, 221, 626 Time variability, light amplification and iability and the individual maser line fea- Gray, M. D. et al. 2016, MNRAS, 456, 374 future plans tures may be as broad as the local ther- Groenewegen, M. A. T. et al. 1999, A&AS, 140, 197 mal width. The 658 GHz single-dish Hirota, T. et al. 2016, ApJ, 817, 168 Molecular line masers, especially the observations do not show spectral fea- Hunter, T. R. et al. 2007, IAU Symposium, 242, 471 Justtanont, K. et al. 2012, A&A, 537, 144 22 GHz H2O line, often exhibit time varia- tures as narrow as the expected thermal Kerschbaum, F. & Olofsson, H. 1999, A&AS, 138, 299 bility and narrow spectral features, result- line widths because the multiple 658 GHz Kim, J. et al. 2010, ApJS, 188, 209 ing from the population inversion and velocity–blended components forming Kim, J. et al. 2014, AJ, 147, 22 radiation amplification mechanisms. the overall line profile within the 9-arcsec- Menten, K. M. & Young, K. 1995, ApJ, 450, L67 Richards, A. M. S. et al. 2014, A&A, 572, L9 These properties are not immediately ond beam of APEX remain unresolved. Spinrad, H. & Newburn, Jr. R. L. 1965, ApJ, 141, 965 obvious with our single-dish observations These components can only be sepa- Teyssier, D. et al. 2012, A&A, 545, 99 of the 658 GHz line. In two well-studied rated by mapping their emission (for Winters, J. M. et al. 2002, A&A, 308, 609 cases, VY CMa and W Hya, which have example, VY CMa; Richards et al., 2014). been observed over more than 20 years, Links the emission line profiles have remained Our APEX results suggest that strong stable and asymmetric, though there is a 658 GHz line sources could be mapped 1 CLASS software package: http://www.iram.fr/ regular decline of the peak intensity in the with ALMA to reveal the details of the kin- IRAMFR/GILDAS VY CMa observations. In Baudry et al., ematics and the small-scale clumpiness (2018) we also showed that, by compar- of stellar winds within the dust formation 13 ing the ratio of the H2O(658) to CO(6–5) zone and beyond. In the case of the integrated intensities nearly six years supergiant VY CMa, ALMA showed that apart, we could not reconcile the meas- the 658 GHz emission extends further urements in three stars (o Ceti, IK Tau out of the dust formation zone. However, and W Hya). This suggests time variability we do not know if this property, which at 658 GHz and, indirectly, maser action likely traces shocks in the stellar enve- — since the high-J 13CO broad line profile lope, is specifically due to its exception- related to circumstellar expansion should ally strong winds (VY CMa’s mass loss not change rapidly. rate ~ 2 × 10–4 M yr –1). 658 GHz images obtained at different epochs for some The 658 GHz line width of individual sources could also tell us how gas masers depends on the light amplification clumps evolve with time, which ones regime within the material in which the show variable activity, and more gener-

H2O population is inverted. If the radiation ally, how stellar winds evolve. Finally, we grows with the exponential of the note that this transition may be suitable 658 GHz opacity as expected for unsatu- for ALMA Band 9 phase calibration, given rated masers, we may observe rapid time the relatively simple line shapes and variability and line features that are strength of the 658 GHz emission in stars smaller than the local thermal line width. for which coordinates are well known. At the other extreme, maser saturation Compact (< 0.35 arcseconds) and strong corresponds to an intrinsic maximum 658 GHz emission was detected towards resulting in little or no time var- the massive protostar Orion Source I in

The Messenger 171 – March 2018 41 Astronomical News Astronomical ESO/D. Mégevand ESO/D.

Upper: The ESPRESSO instrument achieved first light combining the light from all four 8-metre Unit Telescopes in February. The ESPRESSO team marks the occasion with the ESO Director General here.

Lower: Students take part in ESO’s Winter ­Astronomy Camp 2017, which took place between 26 December and 1 January. ESO/Nikki Miller ESO/Nikki

42 The Messenger 171 – March 2018 Astronomical News DOI: 10.18727/0722-6691/5068

New President of Council

Willy Benz1

1 University of Bern & National Centre

of Competence in Research PlanetS, Bella Della Alessandro Switzerland

Is there an astronomer who has not dreamt of being actively involved in the development of world-class astronomical facilities, including the building of the largest telescope ever? This is the fantas- tic opportunity that has been offered to me by the ESO Council following my election as President of this body in late 2017. This is an incredible honour, a huge responsibility and the cause of some ­anxiety, but I also feel a genuine eager- ness to get started. So many challenges lie ahead, but the organisation is strong thanks to several factors: its extraordinary Unsurprisingly, Switzerland is quite dif­ the decision and decided to submit our staff; the dedication of Member States ferent from the USA and it took us all idea in response to the call. We eventu- to work for its success; and the strong some time to re-adjust. After a few years, ally assembled a consortium and sub­ engagement of the community at large I became director of the Physics Institute, mitted the proposal in June 2012. Our at all levels. These constitute a strong a job that I held for thirteen years. During proposal was selected against 25 other recipe for success, and are good reasons that time, I also got involved in my first proposals that October, and I was subse- for me to be confident. ESO project, the High Accuracy Radial quently appointed Principal Investigator velocity Planetary Searcher (HARPS). of the mission, which involves institutes I grew up in Neuchâtel, a small town in More recently, I had the chance to join in 11 ESA member states. Life is unpre- the French-speaking part of Switzerland, new ESO projects such as the Échelle dictable. Unsurprisingly, this project where I studied physics. I later obtained SPectrograph for Rocky Exoplanet and has taken a lot of my time during the last my PhD in astronomy under the guid- Stable Spectroscopic Observations five years, but the launch is scheduled ance of Michel Mayor at the University of (ESPRESSO), the Near Infra Red Planet for early 2019 and science is now on the Geneva and then moved to the USA on Searcher (NIRPS) and even the proposed horizon! a one-year fellowship from the Swiss Extremely Large Telescope (ELT) instru- National Science Foundation. I ended ment, HIRES. Having started as a theorist, While all these activities were going on, up staying for thirteen years — life is I didn’t play a leading role in these pro- we managed to establish the Center for unpredictable. A postdoctoral position jects but supported their construction Space and Habitability at the University at Los Alamos National Laboratory fol- with the help of our engineers. of Bern in 2011, and, in 2014, a National lowed, and I then became junior faculty Centre for Competence in Research at Harvard University and senior faculty In 2008, a few colleagues and I started (NCCR) in planetary sciences, called at the University of Arizona. My scientific playing with the idea of building the PlanetS, of which I am now the director. interests were quite broad, ranging from CHaracterising ExOPlanets Satellite Bringing together all the key players in understanding the origin of our Moon (CHEOPS), a small Swiss satellite dedi- this field across Switzerland, this centre to the physics of supernova explosions. cated to measuring the radii of known has provided scientists in the country Eventually, I focused on the origin and planets orbiting bright stars using the with new research opportunities, includ- evolution of planets within and outside transit method. Unfortunately, a one-year ing the means to participate in ESO the solar system. feasibility study concluded that the mis- instrumentation projects (for example, the sion was too ambitious to be carried out Enhanced Resolution Imager and Spec- In 1997, I was offered a professorship in by Switzerland alone. trograph [ERIS] and NIRPS). the Physics Institute of the University of Bern and my whole family returned to The project took on a new dimension My excursion into the European Space Switzerland. While my wife and I had left with the decision in 2012 by the Euro- Programme has not prevented me from home with two suitcases and our 20- pean Space Agency’s (ESA) Space Pro- keeping close ties with ESO. It is simply month old daughter Sophie, we returned gramme Committee to establish small- impossible to move away from such an with one container, two additional daugh- class missions. As chairman of the Space organisation! Eventually, I had the privilege ters, Florence and Melanie, Coal the dog, Science Advisory Committee, I had care- of serving on two visiting committees, and Leo the cat! fully followed the discussions leading to and in between, to chair the Science and

The Messenger 171 – March 2018 43 Astronomical News

Technical Committee over the period dur- the existing world-class observatories ­General and I are aware of this situation ing which Laurent Vigroux and then Xavier (La Silla Paranal Observatory and the and, together with Council, we will regu- Barcons presided over Council. These last Atacama Large Millimeter/submillimeter larly revisit and monitor these issues, three years, I have been one of the two Array) operational, up-to-date and at the including the general work-life balance at members of Council representing Switzer- forefront of ground-based astronomy. ESO, over the coming years. land — a time during which I could learn the inner workings of the Council and The challenges are not solely of a finan- We have given ourselves fantastic chal- appreciate the exemplary leadership pro- cial nature. Just two examples include lenges that we now must overcome. We vided by its President ­Patrick Roche. finding staff with the specific qualifica- have prepared ourselves to the best of tions needed, and managing large pro- our abilities to tackle them effectively and I don’t think it will come as a surprise to jects across the world. Furthermore, in a in a timely manner. With the organisation, anyone to hear that the organisation is financially constrained environment, the the Member States and the community facing significant challenges. These result workload and the associated stress on we have assembled a winning team. I am from embarking on the building of the everyone, from the Director General to all looking forward to working with everyone ELT, the largest telescope ever con- the staff, including everyone’s families, to continue building this world-leading ceived, while at the same time keeping have risen significantly. The Director astronomical organisation.

DOI: 10.18727/0722-6691/5069

Review of the Last Three Years at ESO

Patrick Roche1

1 Oxford University, UK

I completed my three-year term as ­President of the ESO Council at the end of December 2017. This is therefore an appropriate point at which to review Council’s activities over this period and to reflect on how ESO’s programme has moved forward.

ESO is an evolving organisation, in terms of its Member States as well as its scien- tific and technical programmes and its organisational structure. Poland became the fifteenth Member State when the for- mal accession process was completed in 2015. In 2017, Australia entered into a strategic partnership with ESO, providing Working with the Director General, Council meetings, which are often hosted by a Australian astronomers with access sets the policy and strategy for ESO while Member State. I am very grateful to the to the La Silla–­Paranal facilities for a dec- Council delegates work closely with their hosts of these meetings, which afford ade, whilst opening up the possibility ministries, science communities and the opportunities to meet representatives of of moving towards full membership in due ESO executive towards realising the the scientific communities and funding course. There was also good progress agreed strategy. Council normally meets agencies, and to learn more about with the accession of Brazil through its four times a year, with two formal meet- national activities as well as undertaking parliamentary process in 2015, but the ings usually held at the Garching HQ and Council business. procedures have not been completed. two less formal Committee of Council

44 The Messenger 171 – March 2018 A real strength of ESO is the support and focus of the VLT in preparation for the ture and the major optical and mechan- commitment to the programme provided second-generation VLTI instruments ical structures of the telescope. At the by the Member States, who have agreed and the Échelle SPectrograph for Rocky same time, Council has maintained the not only to fund the ELT construction Exoplanet and Stable Spectroscopic momentum of the project by agreeing whilst maintaining the current facilities as Observations (ESPRESSO) have been a schedule with first light in 2024 and forefront scientific instruments, but also completed. Initial results from the adap- adding all of the primary mirror seg- to provide support for the technology, tive optics assisted, two-object, multi- ments to the approved first phase of the instrumentation and science programmes ple-beam-combiner VLTI instrument telescope. The ELT is a very challenging in national institutes and organisations. GRAVITY indicate that precision astro- project, but progress to date has been This support is being provided at a time metric measurements that will open impressive. Council is fully supportive when many Member States have con- up new opportunities are within reach, and is looking forward to the beginning strained domestic programmes, and with new capabilities imminent when of the site works on Cerro Armazones reflects the importance placed on ESO’s MATISSE and ESPRESSO are early in 2018. facilities and the close collaborations with commissioned. the national communities. There have been many other achieve- – The completion of the Residencia for the ments, including instrument upgrades, In addition to the Council meetings, I Atacama Large Millimeter/submillimeter anti-obsolescence programmes, software have attended a number of other ESO Array (ALMA) and its handover for oper- developments, upgrades to administrative meetings and workshops and have val- ations in 2017 marked the completion processes, amendments to procurement ued the opportunities that they provide of ESO’s contributions to ALMA con- rules and staff benefits and regulations, to meet staff and learn more about the struction. The stunning science results approval and monitoring of budgets, and extent and depth of ESO’s activities. I obtained to date demonstrate that ALMA interactions with potential new Member have especially valued attending the is indeed the transformational facility we States and other institutes and organisa- ESO Annual Overview, which reveals the hoped it would be and that it will meet tions around the world. All of these activi- strength and depth of activities across its design goals. A vision for the further ties are essential in underpinning ESO’s the organisation and the commitment of development of ALMA’s capabilities mission to provide front-line observational the staff to excellence. over the next decade has been agreed capabilities and to foster cooperation in by the ALMA Board; it will lead to greater astronomical research. They rely on the There are many aspects of ESO’s pro- instantaneous bandwidth and higher talent, dedication and hard work of many gramme to note and celebrate. The ESO sensitivity as a high priority, guarantee- people at ESO and at institutes and press releases, webpages and editions ing that ALMA will continue to meet organisations in the Member States and of the Messenger showcase many of the community expectations. beyond, as well as the support and outstanding science results that have cooperation of the Republic of Chile. been obtained, but I want to highlight a – New instruments for the 3.6-metre and few of them here: NTT telescopes at La Silla have been I would like to take this opportunity to selected, securing their futures for the thank everyone who has contributed to – Commissioning activities of the Very next decade and ensuring that La Silla ESO’s outstanding programme over the Large Telescope (VLT) second-genera- remains the natural place to host last three years. I have worked closely tion instruments, KMOS, SPHERE and national facilities and experiments. with many dedicated people and have MUSE, have been completed, and are benefited greatly from their support and currently ongoing for several others – The education and Public Outreach advice. completed his (for example, GRAVITY, MATISSE and programmes have continued to show- ­ten-year mandate as Director General at ESPRESSO). These instruments equip case the output from ESO’s observato- the end of August 2017. This occasion the telescopes with an unparalleled ries and to encourage participation in was marked by a conference that high- suite of powerful instruments for astro- science and technology. A very visible lighted ESO’s achievements over the last nomical discovery. The ensuing scien- sign of this activity is the Supernova decade. It was a truly impressive account tific results continue to push our under- Planetarium & Visitor Centre. The build- of ESO’s activities and its position as the standing of a wide range of astronomical ing has been completed and the exhib- world’s leading observatory, as well as objects and phenomena. The devel­ its are now being installed in preparation Tim’s contributions to that. Xavier Barcons opment of the Adaptive Optics Facility for operation in 2018. The Supernova has taken over as Director General and continues to progress, and the intro- building resulted from a very generous is working hard to ensure that ESO’s pro- duction of further operational modes donation by the Klaus Tschira founda- grammes remain on track and that the will be very important in gaining experi- tion and is a landmark facility that will organisation continues to perform at the ence for future developments and further extend ESO’s reach. highest level. ­operating ESO’s Extremely Large Teles­ cope (ELT). – Following approval of the first phase of I am delighted that Willy Benz has taken the construction of the ELT by Council on the role of Council President, and I – The modification and development at the end of 2014, ESO has moved for- believe that the ESO programme is in of the infrastructure in the combined ward with contracts for the infrastruc- good shape as well as in very good hands.

The Messenger 171 – March 2018 45 Astronomical News DOI: 10.18727/0722-6691/5070

Report on the ESO Workshop QUESO: Submillimetre/Millimetre/Centimetre Q & U (and V )

held at ESO Headquarters, Garching, Germany, 25–27 October 2017

Paola Andreani1 Robert Laing2 Hau-Yu Lu1

1 ESO 2 Square Kilometre Array Organisation, Jodrell Bank Observatory, Manchester, UK

Polarised emission encodes essential physical information about many com- ponents of the Universe, ranging from dust grains and magnetic fields in molecular clouds, protoplanetary discs and evolved stars, through to the for- mation and propagation of relativistic outflows in Active Galactic Nuclei, and to the effects of inflation and primordial frequencies approaching 1 THz for the Figure 1. Participants at the QUESO Workshop gravitational waves on Cosmic Micro- first time. ­photographed in front of the ESO Library. wave Background (CMB) anisotropies. The aim of this workshop was to bring The meeting began with two extended magnetohydrodynamic effects such as together current and future ALMA users, presentations by George Moellenbrock magnetic braking. observatory calibration experts and soft- and Ivan Marti-Vidal on polarimetric tech- ware developers from a broad range of niques for high-frequency interferometry. Polarimetry also complements total-­ research fields making use of polari- These presentations summarised the intensity imaging of protoplanetary disks. metric techniques in the frequency range techniques of interferometric polarimetry, From the fitting of ALMA polarimetric data between approximately 5 and 1000 GHz. data calibration and interpretation, and from 0.87 to 3 mm in the archetypal disc This range was deliberately restricted in novel algorithms developed for the new around HL tau, Akimasa Kataoka infers order to focus attention on common generation of interferometers. Synthesis that the grain sizes are much smaller than problems and to promote cross-fertilisa- instrumental polarisation calibration fun- those derived from the total intensity tion between different subject areas. The damentals for both linear (ALMA) and spectrum alone, with important implica- meeting provided an opportunity for the ­circular (JVLA) feed bases were reviewed, tions for planet formation. polarimetric community to develop col- with special attention paid to practical laborations, understand the latest tech- problems affecting modern instruments. Liz Humphreys and Helmut Wiesemeyer nological developments and decide on outlined how strong masers (SiO, H2O common priorities for the future. A major theme of the meeting was the and OH) are observed in cool evolved unique role of polarimetric observations stars. The maser emission can display a in constraining the magnetic fields in high degree of circular and linear polari- Observing centimetre- or millimetre-wave regions of star formation at high mass — sation, revealing information about the polarised radiation at very high angular by Heshou Zhang, Katherine Pattle, magnetic field strength and morphology, resolutions and sensitivities typically ­Archana Soam and Thushara Pillai — and which are dynamically important in the involves the use of interferometric tech- at low mass — by Anaelle Maury, Maud circumstellar envelopes, and which fall niques. Modern instruments can now Galametz and Valeska Valdivia. Massive off with radius as expected for a toroidal enable full polarisation imaging at unprec- filaments are magnetised and the mag- geometry. Magnetic fields may also drive edented sensitivity over wide instanta­ netic field may be as important as tur­ the shapes of the AGB stars to highly neous bandwidths. Polarisation observa- bulence and gravity. Different methods axisymmetric/aspherical planetary tions have become routine at the Karl G. for estimating the field strength (the nebulae. Jansky Very Large Array (JVLA) as well Chandrasekhar-Fermi method and as other modern observational facilities in ­Zeeman splitting) are valid in different The meeting also covered extragalactic the centimetre, millimetre, and sub­milli­ regimes and therefore difficult to cross- applications. The measurement of Faraday metre bands, and they will increasingly check. Polarimetric observations may rotation at millimetre wavelengths in the become important for the Atacama Large potentially bring new insights into impor- cores of AGN is emerging as an impor- Millimeter/submillimeter Array (ALMA). It tant micro-physics, such as the efficiency tant probe of the accretion rate, following is particularly exciting to note that ALMA’s of grain alignment by magnetic fields, early work on the Galactic Centre. Detec- excellent site will allow interferometric ­anisotropic radiation fields and molecular tions were presented for M87 and 3C273 polarisation observations to be made at gas flows. Further studies would then by Keichi Asada and Talvikki Hovatta, enable more robust investigations of and Hiroshi Nagai noted that the non-­

46 The Messenger 171 – March 2018 Astronomical News

detection in Centaurus A may be a con- ­subtraction) and technical (improved lens All of the presentations are linked on the sequence of orientation. materials for millimetre-wave receivers). meeting website1 and are available through the SAO/NASA Astrophysics An old problem, relevant to both AGN jets The meeting served a valuable purpose Data System database. and star formation, is how to distinguish by identifying priorities for future develop- between vector-ordered and disordered ments in instrumentation. In rough order but anisotropic field topologies, as both of importance, these were agreed to be: Demographics are capable of producing high degrees of − Very accurate circular polarisation cali- polarisation. Carole Mundell considered bration in continuum and line (Zeeman There were 62 registered participants at both topologies in her discussion of AGN effect). the workshop (Figure 1), three quarters of and gamma-ray burst sources. Monica − Improved efficiency of polarisation these coming from European institutions. Orienti pointed out that the degree of ­calibration, avoiding the need for large One-third of all participants were women, field ordering may also help to distinguish parallactic angle rotation during an and a similar fraction were early-career between particle acceleration mecha- observation. researchers, i.e., Masters and Doctoral nisms, for example in hot spots of radio − Wider frequency coverage (for example, students or junior postdoctoral scientists. galaxies. extending polarisation observations to the ALMA Bands 8–10). Although the main theme of the workshop − Lower systematics for measurement of Acknowledgements was interferometric imaging of polarisa- linear polarisation, both to measure This event received funding from the European tion, observations of the CMB with bolo- polarisation fractions < 0.1 % in Union’s Horizon 2020 research and innovation metric arrays were also discussed by protoplanetary discs and to achieve ­programme under grant agreement No 730562 Sean Bryan. There are well-known and high dynamic range for total intensity. [RadioNet] and from ESO. We are grateful to Elena exciting applications of CMB observa- − Polarisation calibration over the primary Zuffanelli for her help with the meeting organisation. tions, including the potential detection beam, for example using Mueller matrix of cosmological B-modes, but also a methods. This is essential for ALMA Links number of synergies, both observational polarisation mosaics. 1 (polarised point sources, foreground QUESO Programme: https://www.eso.org/sci/ meetings/2017/QUESO2017/program.html

DOI: 10.18727/0722-6691/5071 Report on the MOSAIC Science Colloquium Spectroscopic Surveys with the ELT: A Gigantic Step into the Deep Universe

held at the Toledo Congress Centre, Toledo, Spain, 17–19 October 2017

Chris Evans1 The Phase A design of MOSAIC, a capability of the ELT, able to harness Mathieu Puech2 ­powerful multi-object spectrograph its unprecedented sensitivity to deliver François Hammer2 intended for ESO’s Extremely Large unrivalled surveys of the Universe. The Jesús Gallego3 ­Telescope, concluded in late 2017. MOSAIC design combines high-multiplex Ainhoa Sánchez3 With the design complete, a three- near-infrared and visible spectroscopy, Lucía García3 day workshop was held last October together with adaptive optics (AO) spec- Jorge Iglesias4 in Toledo to discuss the breakthrough troscopy in the near infrared that exploits spectroscopic surveys that MOSAIC the fantastic angular resolution of the ELT can deliver across a broad range of across a large field of view. 1 UK Astronomy Technology Centre, contemporary astronomy. Royal Observatory Edinburgh, UK The workshop opened with the latest 2 GEPI, Observatoire de Paris, France news on the ELT project from the ELT 3 Universidad Complutense de Madrid, ESO’s Extremely Large Telescope (ELT) Programme Scientist, Michele Cirasuolo, Spain will be the world’s largest optical/infrared and with overviews of the scientific moti- 4 Instituto de Astrofísica de Andalucía facility for at least a generation. It will vations and technical design of MOSAIC, (CSIC), Spain have an immense collecting area, equiva- which were presented by François lent to gathering together all the current ­Hammer and Myriam Rodrigues. These large telescopes in use today. Multi- were followed by talks that helped set object spectroscopy (MOS) will be a key the scene of the broader landscape in the

The Messenger 171 – March 2018 47 Astronomical News

Figure 1. Workshop ­participants assembled in the Toledo Congress Centre. Carlos Tapia, UCM

mid-2020s, including Luca Pasquini pre- In addition to the contributed talks on After the meeting, participants had an senting future developments at ESO’s recent results and ideas for MOSAIC opportunity to visit the historic Marqués La Silla Paranal Observatory, Andrew ­surveys, the programme featured invited de Valdecilla library of the Universidad Hopkins talking about the innovative and contributed talks on detailed MOSAIC Complutense de Madrid (UCM) in Madrid, ­TAIPAN survey underway on the UK simulations using the Websim-Compass followed by an event presenting the Schmidt telescope and Suresh Sivanan- simulator (Puech et al., 2016), including: MOSAIC concept to national media and dam describing plans for an AO-fed MOS the first galaxies (Karen Disseau); galaxy senior officials of the Spanish Ministry at the Gemini Observatory. rotation curves and dark matter (Jianling and UCM. Wang); intergalactic medium tomography The ensuing science sessions spanned (Jure Japelj); high-redshift dwarf galaxies the diverse and wide-ranging topics that (Arjan Bik); and extragalactic massive Demographics MOSAIC will address, namely the first stars (Oscar Ramírez-Agudelo). galaxies and active galactic nuclei, galaxy In total there were 75 participants (52:23 evolution, the intergalactic medium, extra- Thinking about future ELT surveys, the male:female), 20 invited presentations galactic stellar populations, and Galactic final discussion focused on those that (14:6 male:female), and 17 contributed surveys. The sessions featured invited will be truly unique as they are not possi- talks (11:6 male:female), with a good mix talks on the latest science results and ble with other facilities. Participants con- of senior and junior faculty and early-stage ­relevant instrumentation developments. verged on four key science cases which researchers. For example, Emma Curtis-Lake pre- are potentially the most transformational sented plans for Guaranteed Time Obser- and which will influence future decisions vations of high-redshift galaxies with the in instrument development. These are: Acknowledgements James Webb Space Telescope (JWST); − First-light galaxies: Lyman- emitters α The organisers would like to thank Red de Armando Gil de Paz provided tantalising and physical properties; ­Infraestructuras de Astronomía (RIA) in Spain glimpses of the first observations from − Inventory of matter: baryons and dark and CNRS-INSU in France for financial support the new Gran Telescopio Canarias (GTC) matter; toward the meeting. instrument, Multi-Espectrógrafo en GTC − Extragalactic stellar populations: de Alta Resolución para Astronomía evolved populations beyond the Local References (MEGARA); Olivier le Fèvre reflected on Group; lessons learned from past high-redshift − Evolution of dwarf galaxies: formation, Puech, M. et al. 2016, Proc. SPIE, 9908, 9P surveys and future aspirations with the evolution and contribution to JWST and ELT; Oscar Gonzalez talked reionisation. Links about future surveys of the Milky Way bulge with the VLT third-generation instru- The meeting helped to demonstrate the 1 MOSAIC meeting webpage, including links to the ment, Multi Object Optical and Near-­ high levels of enthusiasm and significant presentations: https://www.mosaictoledo.org 2 Further information and contact details are avail­ infrared Spectrograph (MOONS) and demand for MOS observations on the able at: http://www.mosaic-elt.eu MOSAIC; and finally there were results ELT. Ahead of the start of Phase B of 3 The WEBSIM-COMPASS simulator for MOSAIC from the ESO Public Surveys carried out instrument development, the advanced observations: http://websim-compass.obspm.fr on the VLT MOS instrument VIMOS — simulations presented in Toledo will be Large Early Galaxy Astrophysics Census published, and new topics identified in (LEGA-C) and VANDELS, which were the meeting will also be investigated in presented by Arjen van der Wel and greater detail. Laura Pentericci, respectively.

48 The Messenger 171 – March 2018 Astronomical News DOI: 10.18727/0722-6691/5072

Fellows at ESO

Darshan Kakkad Darshan Kakkad

It’s a pleasant summer night in Paranal; it just rained and we put the covers over the primary mirror at Unit Telescope 4 (also known as Yepun) for protection. The telescope domes are now closed and all of us are waiting until the weather improves. And here I am, sitting in the control room in the middle of the Atacama desert and, even more than the reader, I myself am wondering how the choices in my life got me here! None of my family members work in areas even remotely related to science. To them, I am the guy who looks through a small telescope in his backyard searching for aliens. The fellowship continued as long as I did work, especially the feeling of having a research project in any institution in solved a problem after some months. My story begins with a power cut in Delhi. India each year during the summer. I vis- It used to happen quite frequently on ited the Giant Metrewave Radio Tele- Since my PhD, I have been heavily summer nights and the terrace in my scope (GMRT) facility as part of this fel- involved in integral field spectroscopy house used to be the best place to get lowship to do a project on testing the and sub-millimetre spectroscopy at both cool breezes. I was in middle school new broadband feeds using pulsars. After low and high redshifts. Using a multi- back then and, along with my siblings, a two-hour bus journey from the city of wavelength approach, I investigate we used to look at the stars and try to Pune through the lush, green landscape, whether the presence of ionised outflows identify the that we had I started spotting the antennas one after in the host galaxies of X-ray selected learnt at school. Perhaps that was the the other as we entered the observatory. AGN has an impact on the global proper- first time I was interested in becoming Once there, my cellphone would be ties of the host galaxy, such as the star an astronomer, although crediting Delhi switched off for two full months, apart formation rate, molecular gas mass or power cuts does not seem the best from during the occasional trips when I gas densities. I have been using data “how I got inspired” story! I still remember would go back into the city. Although from the Spectrograph for INtegral when I got up early in the morning in my first observing run was a disaster, Field Observations in the Near Infrared 2005 and ran to the same terrace to see with no useful data acquired, the entire (­SINFONI) at the VLT, the Wide-Field the sunrise — or rather, the eclipsed learning experience was something I Spectrograph (WiFeS) at the Australian ­sunrise. It was probably the best eclipse enjoyed and I was sure of pursuing a National University (ANU) and the I have seen in my life: the red Sun at the PhD in Astronomy after that. Atacama Large Millimeter/submillimeter horizon covered by the Moon. Array (ALMA) for this purpose, collabo­ I was therefore excited to get an offer rating with people at ESO, the ANU, the The seed was planted and all it required from ESO as part of the International Istituto Nazionale di Astrofisica (INAF) was some nourishment and a bit of luck. Max Planck Research School (IMPRS) in Italy and various institutions in Japan I was adamant about pursuing a career PhD school in Munich where I would and the UK. As an ESO fellow, I am related to space and/or astronomy. After change topics to work on active galactic ­continuing to work in this field with more high school, I even went to a selection nuclei (AGN) feedback with Vincenzo diverse and deeper data sets. camp for the Indian Air Force in hopes of Mainieri and Paolo Padovani. The thought becoming a pilot (and, eventually, an of working with data from one of the best Working with data is amazing in itself, astronaut: Teenage Dreams!). However, telescopes in the world was fascinating but as a person who aspires to be an I was kicked out on the fifth day of selec- and I could not wait to get started after astronomer, I felt it was important to have tion. As nowhere in India offered an my masters degree. Having limited expe- the experience of working in the place undergraduate degree in astronomy, I rience with observational astronomy, I where the real action happens — the decided to settle for physics at the Univer- had a steep learning curve at the begin- Observatory itself. I was keen to see how sity of Delhi for my bachelor programme. ning of my PhD. There is a huge differ- instruments work and experience the During the first year of my undergradu- ence between doing a two-month intern- challenges that can occur when taking ate course, I got a Kishore Vaigyanik ship and a PhD, where solving problems observations. This is what motivated me Protsahan Yojana (KVPY) fellowship from sometimes takes a year. Also, coming to join ESO for a fellowship in Chile and, the Department of Science and Technol- from a tropical environment, I wasn’t famil- indeed, the experience at the Paranal ogy of India, which secured my education iar with the white thing they call “snow”. Observatory is completely different com- funding until the end of a masters degree. So, climate-wise as well, it took me time pared to sitting in a chair and looking at to get used to the colder weather. the data. It’s just amazing how dedicated Despite these differences, I enjoyed my people at the Observatory are to solving

The Messenger 171 – March 2018 49 Astronomical News

issues each day in order to have the tele- Elizabeth Bartlett scope ready for the observations every night.

And that’s what we are doing right now! It’s almost 2am. The rain has stopped and the weather officer has given the clearance to open the domes. The tele- scope operators have put on their hel- mets to go to the Unit Telescopes and start the opening sequences and within a few minutes we will start observing again. We’re all happy to have managed even three hours of observation over the night. People say, “Time is Money”. Well over here, “Time is Science!” tution at the time, the course included these sources, both individually and as a the opportunity to visit and take data at a population. I used simultaneous X-ray Elizabeth Bartlett “real” observatory, the Observatorio del spectral and timing analysis to constrain Teide in Tenerife, home of the Instituto de system geometries, and worked on In 1995, when I was seven or eight years Astrofísica de Canarias 80-centimetre ­identifying new high-mass X-ray binary old, my mum picked up a book called (IAC-80) telescope. I remember arriving candidates by cross-correlating searches Skywatch for a couple of pounds in a at the observatory after dark, getting off of X-ray sources with optical, radio and local supermarket. The book had a page the bus and really seeing the night sky infra-red catalogues, and developing of information on each planet, as well for the first time — that’s when I knew I techniques that make use of multi-wave- as galaxies and different types of stars, wanted to be an astronomer. The module length data to discriminate between along with some pictures and artists’ was about more than just inspiring us; we ­different types of sources. This multi- impressions of celestial objects. I often learnt about right ascension, declination wavelength project was particularly wonder what would have happened if my and hour angles, how to plan an observ- appealing as it allowed me to combine mum had walked past that book or had ing run, CCDs, data calibration, and most my newly gained skills and knowledge in picked up something different instead; crucially, how to get along with everyone X-ray astronomy with my passion for the that book set me on a journey that has at 2400 m in a snowstorm! While my night sky. My supervisor promised me taken me around the world and currently other astronomy modules taught me the several observing trips, and he delivered, has me sitting in Santiago (Chile) after physics behind the greatest astronomical with yearly visits to the South African a shift at ESO’s Very Large Telescope. discoveries, this module taught me how Astronomical Observatory (SAAO) to use these discoveries came about, from data the 74-inch Radcliffe telescope and a If that book dug the foundations for my to the resultant paper. trip to ESO’s La Silla observatory to use future career, then the concrete was the New Technology Telescope. set by seeing comet Hale Bopp just a I spent the final year of my degree pro- couple of years later through my grand­ gramme at the Harvard-Smithsonian After my PhD I moved to South Africa to father’s small refracting telescope (usually Center for Astrophysics (CfA) in Boston. take up a Claude-Leon research fellow- used for watching passing ships). Eager Here, I did the research for my Masters ship at the University of Cape Town. I to fuel this obsession of mine, my grand- thesis in the High Energy Astrophysics expanded my work to cover other X-ray father bought me every single astronomy Division with Michael Garcia, attempting emitting massive binaries, such as collid- book he found in a charity shop or car to do proof-of-concept for X-ray timing ing wind binaries, and became heavily boot sale, right up until the day he died. techniques with data from the X-ray Multi-­ involved with the Southern African Large This led to an eclectic personal library, Mirror satellite (XMM-Newton) ahead of Telescope (SALT) — technically the big- ranging from that first “Skywatch” book, the, now cancelled, International X-ray gest single telescope in the Southern right up to an advanced level textbook Observatory. Working at the CfA gave me Hemisphere. I established a dedicated about planetary atmospheres, which a taste for the more day-to-day aspects campaign to monitor the X-ray bright was way beyond my understanding at of life as an astronomer, and working with supergiant emission-line sgB[e] stars in 12 years old! high-energy space-based data brought the Magellanic clouds, and was also a completely different set of challenges. involved in the testing and development My passion for astronomy remained with of the SALT data pipeline and PySALT me throughout school, but I had no idea I returned to Southampton for my PhD, python-based software package. SALT that astronomy could be an actual career to work with Malcolm Coe as part of shares the SAAO site with smaller tele- path until I went to university. I studied the X-ray binary group, monitoring the scopes, so while observing on the Physics and Astronomy at the University Magellanic Cloud population. My research 74-inch telescope I would often run over of Southampton as, unlike any other insti- focused on multi-wavelength studies of to SALT after starting an observation, not

50 The Messenger 171 – March 2018 just to use their coffee machine, but also instrument scientist for FLAMES and to see operations. SALT is only operated enjoy having the opportunity to leave a in service mode and closely follows the mark on Paranal beyond my time here — ESO model (as it is mostly run by ex-ESO or at least until FLAMES gets decommis- fellows, such as, Petri Vaisanen and Eric sioned! I was also fortunate enough to be Depagne). Getting to see my own data at Paranal just after the initial detection of being taken was a treat that few astrono- the gravitational wave GW170817. Being mers get to experience. I have no doubt at the observatory at such a time was an that it was the combination of working absolute privilege (whilst simultaneously closely with SALT and working with the being incredibly stressful!) and the atmos- older, more hands on, telescopes that phere in the control room during those made my application attractive to ESO. nights will stay with me for a long time.

My time in South Africa really opened my The start of Period 101 coincides with the eyes to the power of astronomy for social beginning of my final year of duties at change. Observatories are built in remote Paranal. I have been awarded 20 hours of locations and in developing countries; this X-shooter time to look at my targets in often means near disadvantaged commu- this period and my hope is that I get the nities. To build an observatory you need chance to execute some of my own infrastructure, such as paved roads, elec- observations. That would be a very spe- tricity, water and the Internet. To maintain cial moment for me as my time at Paranal an observatory, you need trained engi- draws to a close and would complete my neers on hand who can fix the telescopes experience as an ESO fellow. Hau-Yu Lu and instruments, and staff to take care of the food and lodging for the astronomers. rough idea to use the spatial distributions World-class telescopes, such as the VLT, Hau-Yu Lu and motions of galaxies in a cluster to generate interest that leads to tourism pro- probe the gravitational potential of the viding a huge boost to local economies. I grew up on a very tropical island in East dark matter, so surveying galaxy groups Observatories can provide employment Asia, Taiwan. I studied at the National or clusters might be a good place to start. across many sectors in regions where ­Taiwan University, where I majored in there may be few opportunities. One physics. One of the focuses of the phys- Following up on this simple idea, I joined could argue that a telescope’s success ics department is on particle physics the group under Tzi-Hong Chiueh in should not just be measured in the num- and several professors in the theoretical ­Taiwan University and was introduced to ber of papers it produces but on how it group were quite stimulating. I particularly Lihwai Lin and Bau-Ching Hsieh, post- enriches the communities that surround it. enjoyed brainstorming sessions on math- doctoral researchers at the Academia ematical physics and used to follow the Sinica Institute of Astronomy and Astro- Now an ESO fellow, I am part of the sci- related group meetings and seminars. In physics (ASIAA). At that point, very mas- ence operations team at Paranal Obser- particular, I was very impressed by the sive galaxy clusters could be identified vatory. I spend 80 nights a year observing culture in the group under Pei-Ming Ho. by either X-ray observations, the Sunyaev- at Kueyen (Unit Telescope 2 [UT2]), the Thanks to that team I have an attitude of Zel’dovich effect, strong lensing, or the home of the UV-Visual Echelle Spectro- constantly questioning myself until I con- photometric red sequence. However, the graph (UVES), the wideband ultraviolet-­ verge on a position that feels self-consist- identification of smaller groups and clus- infrared spectrograph X-shooter and the ent and logical. I also became an efficient ters was ambiguous, largely because of Fibre Large Array Multi Element Spectro- and motivated self-learner and greatly the poor detection limits in relatively shal- graph (FLAMES). While there are many enjoyed my college life. low photometric surveys as well as the observatories around the world that allow poor completeness of redshift samples. one to gain observing experience, I have I quickly realised that I could understand We therefore looked into how to associ- the chance to go beyond this by working theoretical and fundamental physics, ate sparsely sampled galaxies in the red- at ESO’s Paranal Observatory and to be which I greatly appreciated, but found shift domain using an artificial neural net- part of something truly bigger than me or it difficult to be creative when doing work, and benchmarked our algorithms my work. research in these areas. I was capable of based on mock galaxy surveys generated working on phenomenological theories from N-body simulations. Last year I was involved in interventions based on fundamental physics, on the on all three of the instruments on UT2, other hand, but found that the models of When reading papers about how N-body including recovering the resolution of the dark matter and dark energy were only simulations were made, I started to blue arm of UVES and the recommission- loosely constrained by experiments. I ­realise that mock galaxy surveys were ing of X-shooter after it was dismounted started thinking about starting again as too artificial for my purposes. First, and dismantled to repair the atmospheric an observer, although I did not have a there is the artificial criterion that dark dispersion correctors. I am currently the concrete idea about what to do. I had a matter overdensities can be regarded as

The Messenger 171 – March 2018 51 Astronomical News

galaxy-forming dark halos. Then, galaxies accrete, and what is the specific parent service. My research area was signifi- were assigned to individual dark halos molecular cloud morphology that would cantly broadened during that time and I based on the halo occupation distribution permit the subsequent formation of lower got my first masters students, Yuxin Lin function, which is rather empirical. Finally, mass stars. and I-Hsiu Li — of whom I am extremely ­galaxies were assumed to have certain proud — to join my journey to investigate based on yet another empiri- My thesis supervisor was Paul Ho at how amorphous low-density gas clouds cally assumed mass-to-light distribution ASIAA who was leading the SubMillimeter evolve to become OB cluster-forming function. This same mass-to-light distri- Array (SMA) project, which was the most clouds, and to learn where and when bution function plays a critical role in powerful tool that could be used to spa- dust grains grow in a protoplanetary disc. allowing us to relate observations to the tially resolve detailed molecular cloud However, they were apparently too good underlying actual structures. In other structures at that time. For the last three as they ended up being recruited to join words, our conclusions based on obser- years of my PhD, I went on an exchange other researchers’ journeys, which I am vations can be hugely biased if we do not to the Harvard-Smithsonian Center for also very glad about, of course. understand this function. Astrophysics (CfA), to work with Qizhou Zhang. During these years, I had the These same years also coincided with Mass and light are linked by the baryon opportunity to engage more with the the start of science operations for the fraction as well as the “laws” governing SMA community and visited the National Atacama Large Millimeter/submillimeter how high-mass stars form out of baryons. Radio Astronomy Observatory in Socorro Array (ALMA). As ASIAA is a partner insti- Star formation laws exist, but are not for several months during the upgrade tution, I had the opportunity to experi- yet understood from first principles. Not of the NRAO Karl G. Jansky Very Large ence ALMA operations first-hand. All of even close! In fact, even just forming a Array (JVLA). I would specifically like to these experiences formed me and paved luminous OB cluster is a highly non-trivial thank Melvyn Wright at Berkeley, who is the way to my joining ESO as a postdoc- phenomenological problem. This is still teaching me about radio interferome- toral fellow in Garching, as well as turning because the radiative feedback from the try (and writing in English). me into who I am now. I have also con- highest mass stars may destroy the parent tributed to the report on the QUESO 2017 molecular cloud as soon as they form. After my PhD, I returned to ASIAA as a workshop (p. 46) in this issue of the I therefore decided that my PhD thesis postdoctoral fellow, and that period ESO ­Messenger, which you might find of topic was to understand how OB stars also served to substitute for my military interest!

Personnel Movements

Arrivals (1 January–31 March 2018) Departures (1 January–31 March 2018)

Europe Europe

Bezawada, Nagaraja Naidu (UK) Detector Engineer Allaert, Eric (BE) Senior Software Engineer Brandt, Daniel (DE) IT Specialist Database Administrator Ghiretti, Paolo (IT) Civil Engineer Dominguez-Faus, Lidia (ES) Software Engineer Gonzalez Fernandez, Ariadna Irene (ES) Student Gnatz, Amelie (DE) Documentation Specialist Zivkov, Viktor (DE) Student Hucke, Jannett (DE) Internal Auditor Jaillot, Caroline (FR) Electronic Engineer Pathak, Prashant (IN) Fellow Prole, Daniel (UK) Student Sanchis Melchor, Enrique (ES) Student Serra, Benoît (FR) Fellow Tax, Tomas (CZ) Student Vieser, Wolfgang (DE) ESO Supernova Education Coordinator Wallace, Mark (AU) Control Engineer Zanoni, Carlo (IT) Opto-Mechanical Engineer

Chile Chile

Bian, Fuyan (CN) Operation Staff Astronomer Cox, Pierre (FR) Senior Scientist Courtney-Barrer, Benjamin (AU) Telescope Instruments Operator Jaffe Ribbi, Yara Lorena (VE) Fellow Figueira, Pedro (PT) Operation Staff Astronomer Johnston, Evelyn (UK) Fellow Leclercq, Julien (FR) Mechanical Engineer Neumann, Justus (DE) Student Parra, Ricardo (CL) Optical Coating Engineer Slusarenko, Nicolas (CL) Software Engineer

52 The Messenger 171 – March 2018 Annual Index 2017 (Nos. 167–170)

Subject Index Near-InfraRed Planet Searcher to Join HARPS on Three Years of SPHERE: The Latest View of the the ESO 3.6-metre Telescope; Bouchy, F.; Doyon, Morphology and Evolution of Protoplanetary R.; Artigau, É.; Melo, C.; Hernandez, O.; Wildi, F.; Discs; Garufi, A.; Benisty, M.; Stolker, T.; Delfosse, X.; Lovis, C.; Figueira, P.; Canto Martins, Avenhaus, H.; de Boer, J.; Pohl, A.; Quanz, S. P.; The Organisation B. L.; González Hernández, J. I.; Thibault, S.; Dominik, C.; Ginski, C.; Thalmann, C.; van Boekel, Reshetov, V.; Pepe, F.; Santos, N.C.; de Medeiros, R.; Boccaletti, A.; Henning, T.; Janson, M.; Salter, A Long Expected Party — The First Stone Ceremony J. R.; Rebolo, R.; Abreu, M.; Adibekyan, V. Z.; G.; Schmid, H. M.; Sissa, E.; Langlois, M.; Beuzit, for the Extremely Large Telescope; de Zeeuw, T.; Bandy, T.; Benz, W.; Blind, N.; Bohlender, D.; J.-L.; Chauvin, G.; Mouillet, D.; Augereau, J.-C.; Comerón, F.; Tamai, R.; 168, 2 Boisse, I.; Bovay, S.; Broeg, C.; Brousseau, D.; Bazzon, A.; Biller, B.; Bonnefoy, M.; Buenzli, E.; The Strategic Partnership between ESO and Cabral, A.; Chazelas, B.; Cloutier, R.; Coelho, J.; Cheetham, A.; Daemgen, S.; Desidera, S.; Engler, Australia; Comendador Frutos, L.; de Zeeuw, T.; Conod, U.; Cumming, A.; Delabre, B.; Genolet, L.; N.; Feldt, M.; Girard, J.; Gratton, R.; Hagelberg, J.; Geeraert, P.; 169, 2 Hagelberg, J.; Jayawardhana, R.; Käufl, H.-U.; Keller, C.; Keppler, M.; Kenworthy, M.; Kral, Q.; Astronomy in Australia; Watson, F.; Couch, W.; 170, Lafrenière, D.; de Castro Leão, I.; Malo, L.; de Lopez, B.; Maire, A.-L.; Menard, F.; Mesa, D.; 2 Medeiros Martins, A.; Matthews, J. M.; Metchev, Messina, S.; Meyer, M. R.; Milli, J.; Min, M.; Muller, S.; Oshagh, M.; Ouellet, M.; Parro, V. C.; Rasilla A.; Olofsson, J.; Pawellek, N.; Pinte, C.; Szulagyi, Piñeiro, J. L.; Santos, P.; Sarajlic, M.; Segovia, A.; J.; Vigan, A.; Wahhaj, Z.; Waters, R.; Zurlo, A.; Sordet, M.; Udry, S.; Valencia, D.; Vallée, P.; Venn, 169, 32 Telescopes and Instrumentation K.; Wade, G. A.; Saddlemyer, L.; 169, 21 ALLSMOG, the APEX Low-redshift Legacy Survey First Light for GRAVITY: A New Era for Optical for MOlecular Gas; Bothwell, M.; Cicone, C.; The ALMA Science Archive; Stoehr, F.; Manning, A.; Interferometry; Gravity Collaboration; 170, 10 Wagg, J.; De Breuck, C.; 169, 38 Moins, C.; Jenkins, D.; Lacy, M.; Leon, S.; Muller, GRAVITY Science Verification; Mérand, A.; Berger, The Close AGN Reference Survey (CARS); E.; Nakanishi, K.; Matthews, B.; Gaudet, S.; J.-P.; de Wit, W.-J.; Eisenhauer, F.; Haubois, X.; Husemann, B.; Tremblay, G.; Davis, T.; Busch, G.; Murphy, E.; Ashitagawa, K.; Kawamura, A.; 167, 2 Paumard, T.; Schoeller, M.; Wittkowski, M.; McElroy, R.; Neumann, J.; Urrutia, T.; Krumpe, M.; ALMA Band 5 Science Verification; Humphreys, L.; Woillez, J.; Wolff, B.; 170, 16 Scharwächter, J.; Powell, M.; Perez-Torres, M.; Biggs, A.; Immer, K.; Laing, R.; Liu, H. B.; MUSE WFM AO Science Verification; Leibundgut, B.; The CARS Team; 169, 42 Marconi, G.; Mroczkowski, T.; Testi, L.; Yagoubov, Bacon, R.; Jaffé, Y. L.; Johnston, E.; Kuntschner, ALMA Observations of z ~ 7 Quasar Hosts: Massive P.; 167, 7 H.; Selman, F.; Valenti, E.; Vernet, J.; Vogt, F.; 170, Galaxies in Formation; Venemans, B. P.; 169, 48 Report on the ESO Workshop “Getting Ready for 20 Tales of Tails: Gas Stripping Phenomena in Galaxies ALMA Band 5 — Synergy with APEX/SEPIA”; with MUSE; Poggianti, B. M.; Gullieuszik, M.; De Breuck, C.; Testi, L.; Immer, K.; 167, 11 Moretti, A.; Jaffé, Y. L.; Fritz, J.; Vulcani, B.; The Adaptive Optics Facility: Commissioning Astronomical Science Bettoni, D.; Bellhouse, C.; Fasano, G.; Radovich, Progress and Results; Arsenault, R.; Madec, P.-Y.; M.; the GASP collaboration; 170, 29 Vernet, E.; Hackenberg, W.; La Penna, P.; Unveiling the Nature of Giant Ellipticals and their Minor Planet Science with the VISTA Hemisphere Paufique, J.; Kuntschner, H.; Pirard, J.-F.; Kolb, J.; Stellar Halos with the VST; Spavone, M.; Survey; Popescu, M.; Licandro, J.; Morate, D.; Hubin, N.; 168, 8 Capaccioli, M.; Napolitano, N. R.; Iodice, E.; de León, J.; Nedelcu, D. A.; 167, 16 ESO Public Surveys at VISTA: Lessons learned from Grado, A.; Limatola, L.; Cooper, A. P.; Cantiello, Cycle 1 Surveys and the start of Cycle 2; The Nearby Evolved Star L2 as a Portrait of M.; Forbes, D. A.; Paolillo, M.; Schipani, P.; 170, Arnaboldi, M.; Delmotte, N.; Gadotti, D.; Hilker, the Future Solar System; Kervella, P.; Montargès, 34 M.; Richards, A. M. S.; Homan, W.; Decin, L.; M.; Hussain, G. A. J.; Mascetti, L.; Micol, A.; Dissecting the Core of the Tarantula Nebula with Lagadec, E.; Ridgway, S. T.; Perrin, G.; McDonald, Petr-Gotzens, M.; Rejkuba, M.; Retzlaff, J.; Ivison, MUSE; Crowther, P. A.; Castro, N.; Evans, C. J.; I.; Ohnaka, K.; 167, 20 R.; Leibundgut, B.; Romaniello, M.; 168, 15 Vink, J. S.; Melnick, J.; Selman, F.; 170, 40 Supernova 1987A at 30; Spyromilio, J.; Leibundgut, The Cherenkov Telescope Array: Exploring the VLTI Imaging of a High-Mass Protobinary System: B.; Fransson, C.; Larsson, J.; Migotto, K.; Girard, Very-high-energy Sky from ESO’s Paranal Site; Unveiling the Dynamical Processes in High-Mass J.; 167, 26 Hofmann, W.; 168, 21 Star Formation; Kraus, S.; Kluska, J.; Kreplin, A.; Period 100: The Past, Present and Future of ESO VANDELS: Exploring the Physics of High-redshift Bate, M.; Harries, T.; Hofmann, K.-H.; Hone, E.; Observing Programmes; Patat, F.; Hussain, Galaxy Evolution; McLure, R.; Pentericci, L.; Monnier, J.; Weigelt, G.; Anugu, N.; de Wit, W.-J.; G. A. J.; Gadotti, D.; Primas, F.; 169, 5 the VANDELS team; 167, 31 Wittkowski, M.; 170, 45 Scientific Return from VLT instruments; Leibundgut, To be or not to be Asymmetric? VLTI/MIDI and the B.; Bordelon, D.; Grothkopf, U.; Patat, F.; 169, 11 Mass-loss Geometry of AGB Stars; Paladini, C.; Klotz, D.; Sacuto, S.; Lagadec, E.; Wittkowski, M.; NEAR: Low-mass Planets in a Cen with VISIR; Astronomical News Kasper, M.; Arsenault, R.; Käufl, H.-U.; Jakob, G.; Richichi, A.; Hron, J.; Jorissen, A.; Groenewegen, Fuenteseca, E.; Riquelme, M.; Siebenmorgen, R.; M. A. T.; Kerschbaum, F.; Verhoelst, T.; Rau, G.; Sterzik, M.; Zins, G.; Ageorges, N.; Gutruf, S.; Olofsson, H.; Zhao-Geisler, R.; Matter, A.; 168, 28 Report on the “2017 ESO Calibration Workshop: Reutlinger, A.; Kampf, D.; Absil, O.; Carlomagno, Towards a Sharper Picture of R136 with SPHERE The Second-Generation VLT Instruments and B.; Guyon, O.; Klupar, P.; Mawet, D.; Ruane, G.; Extreme Adaptive Optics; Khorrami, Z.; Vakili, F.; Friends”; Smette, A.; Kerber, F.; Kaufer, A.; 167, 37 Karlsson, M.; Pantin, E.; Dohlen, K.; 169, 16 Lanz, T.; Langlois, M.; Lagadec, E.; Meyer, M. R.; Highlights from the CERN/ESO/NordForsk “Gender Gratton, R.; Beuzit, J.-L.; Mouillet, D.; 168, 32 in Physics Day”; Primas, F.; Guinot, G.; 1000 High-redshift Galaxies with Spatially-resolved Strandberg, L.; 167, 39 Spectroscopy: Angular Momentum over 10 Billion Report on the “ESO Python Boot Camp — Pilot Years; Harrison, C.; Swinbank, M.; 168, 36 Version”; Dias, B.; Milli, J.; 167, 42 The VIMOS Public Extragalactic Redshift Survey Fellows at ESO; Sybilska, A.; De Cia, A.; Lillo Box, J.; (VIPERS): Science Highlights and Final Data 167, 4 5 Release; Guzzo, L.; The Vipers Team; 168, 40 SPHERE Sheds New Light on the Collisional History of Main-belt Asteroids; Marsset, M.; Carry, B.; Pajuelo, M.; Viikinkoski, M.; Hanuš, J.; Vernazza, P.; Dumas, C.; Yang, B.; 169, 29

The Messenger 171 – March 2018 53 Personnel Movements; ESO; 167, 48 Report on the EWASS Workshop “EWASS 2017 The ESO Survey of Non-Publishing Programmes; Report on the Workshops “VLTI Community Days” Special Session SS18: The ELT Project Status and Patat, F.; Boffin, H. M. J.; Bordelon, D.; Grothkopf, “VLTI Winter School”; Mérand, A.; 168, 49 Plans for Early Science”; Evans, C. J.; Hook, I.; U.; Meakins, S.; Mieske, S.; Rejkuba, M.; 170, 51 Report on the Workshop “Stellar Populations in Bono, G.; Ramsay, S.; 169, 59 On the Availability of ESO Data Papers on Stellar Clusters and Dwarf Galaxies — Report on the ESO Workshop “The Impact of arXiv/astro-ph; Grothkopf, U.; Bordelon, D.; New Astronomical and Astrophysical Challenges”; Binaries on Stellar Evolution”; Boffin, H. M. J.; Meakins, S.; Emsellem, E.; 170, 58 Dias, B.; Saviane, I.; 168, 50 Beccari, G.; Petr-Gotzens, M.G.; 169, 61 Report on the ESO and Excellence Cluster Universe In Memoriam Giovanni Bignami; de Zeeuw, T.; Forty Years at ESO — Bernard Delabre and Optical Workshop “Galaxy Ecosystem: Flow of Baryons Gilmozzi, R.; 168, 53 Designs; de Zeeuw, T.; Lévêque, S.; Pasquini, L.; through Galaxies”; Mainieri, V.; Popesso, P.; 170, Engineering and Technical Research Fellowship Péron, M.; Spyromilio, J.; 169, 64 61 Programme; ESO; 168, 52 Departure of Patrick Geeraert, Director of Report on the ESO Workshop “Early Stages of Fellows at ESO; Popping, G.; Agnello, A.; 168, 54 Administration; de Zeeuw, T.; 169, 66 Galaxy Cluster Formation 2017 (GCF2017)”; Mroczkowski, T.; Stroe, A.; Andreani, P.; Arnaud, ESO Fellowship Programme 2017/2018; ESO; 168, Jerry Nelson — An Appreciation of his Pioneering M.; Arrigoni Battaia, F.; De Breuck, C.; Sobral, D.; 57 Telescope Work; Spyromilio, J.; Dierickx, P.; 169, 67 170, 63 Personnel Movements; ESO; 168, 59 Fellows at ESO; Plunkett, A.; Yen, H. W.; 169, 68 Fellows at ESO; Messias, H.; Man, A.; 170, 66 The Deadline Flurry Formula; Stoehr, F.; 169, 53 Personnel Movements; ESO; 169, 70 External Fellows at ESO; Oteo, I.; 170, 68 Report on the ESO Workshop “Star Formation from Personnel Movements; ESO; 170, 70 Cores to Clusters”; Plunkett, A.; Comerón, F.; Testi, L.; 169, 58 Message from the Editor; Hussain, G. A. J.; 170, 70

Author Index Bouchy, F.; Doyon, R.; Artigau, É.; Melo, C.; de Zeeuw, T.; Lévêque, S.; Pasquini, L.; Péron, M.; Hernandez, O.; Wildi, F.; Delfosse, X.; Lovis, C.; Spyromilio, J.; Forty Years at ESO — Bernard Figueira, P.; Canto Martins, B. L.; González Delabre and Optical Designs; 169, 64 Hernández, J. I.; Thibault, S.; Reshetov, V.; Pepe, A de Zeeuw, T.; Departure of Patrick Geeraert, Director F.; Santos, N. C.; de Medeiros, J. R.; Rebolo, R.; of Administration; 169, 66 Abreu, M.; Adibekyan, V. Z.; Bandy, T.; Benz, W.; Dias, B.; Milli, J.; Report on the “ESO Python Boot Arnaboldi, M.; Delmotte, N.; Gadotti, D.; Hilker, M.; Blind, N.; Bohlender, D.; Boisse, I.; Bovay, S.; Camp — Pilot Version”; 167, 42 Hussain, G. A. J.; Mascetti, L.; Micol, A.; Broeg, C.; Brousseau, D.; Cabral, A.; Chazelas, Dias, B.; Saviane, I.; Report on the Workshop “Stellar Petr-Gotzens, M.; Rejkuba, M.; Retzlaff, J.; Ivison, B.; Cloutier, R.; Coelho, J.; Conod, U.; Cumming, Populations in Stellar Clusters and Dwarf Galaxies R.; Leibundgut, B.; Romaniello, M.; ESO Public A.; Delabre, B.; Genolet, L.; Hagelberg, J.; — New Astronomical and Astrophysical Surveys at VISTA: Lessons learned from Cycle 1 Jayawardhana, R.; Käufl, H.-U.; Lafrenière, D.; de Challenges”; 168, 50 Surveys and the start of Cycle 2; 168, 15 Castro Leão, I.; Malo, L.; de Medeiros Martins, A.; Arsenault, R.; Madec, P.-Y.; Vernet, E.; Hackenberg, Matthews, J. M.; Metchev, S.; Oshagh, M.; W.; La Penna, P.; Paufique, J.; Kuntschner, H.; Ouellet, M.; Parro, V. C.; Rasilla Piñeiro, J. L.; Pirard, J.-F.; Kolb, J.; Hubin, N.; The Adaptive Santos, P.; Sarajlic, M.; Segovia, A.; Sordet, M.; E Optics Facility: Commissioning Progress and Udry, S.; Valencia, D.; Vallée, P.; Venn, K.; Wade, Results; 168, 8 G. A.; Saddlemyer, L.; Near-InfraRed Planet Evans, C. J.; Hook, I.; Bono, G.; Ramsay, S.; Report Searcher to Join HARPS on the ESO 3.6-metre on the EWASS Workshop “EWASS 2017 Special Telescope; 169, 21 Session SS18: The ELT Project Status and Plans B for Early Science”; 169, 59

Boffin, H. M. J.; Beccari, G.; Petr-Gotzens, M. G.; C Report on the ESO Workshop “The Impact of G Binaries on Stellar Evolution”; 169, 61 Comendador Frutos, L.; de Zeeuw, T.; Geeraert, P.; Bothwell, M.; Cicone, C.; Wagg, J.; De Breuck, C.; The Strategic Partnership between ESO and Garufi, A.; Benisty, M.; Stolker, T.; Avenhaus, H.; de ALLSMOG, the APEX Low-redshift Legacy Survey Australia; 169, 2 Boer, J.; Pohl, A.; Quanz, S. P.; Dominik, C.; for MOlecular Gas; 169, 38 Crowther, P. A.; Castro, N.; Evans, C. J.; Vink, J. S.; Ginski, C.; Thalmann, C.; van Boekel, R.; Melnick, J.; Selman, F.; Dissecting the Core of the Boccaletti, A.; Henning, T.; Janson, M.; Salter, G.; Tarantula Nebula with MUSE; 170, 40 Schmid, H. M.; Sissa, E.; Langlois, M.; Beuzit, J.-L.; Chauvin, G.; Mouillet, D.; Augereau, J.-C.; Bazzon, A.; Biller, B.; Bonnefoy, M.; Buenzli, E.; D Cheetham, A.; Daemgen, S.; Desidera, S.; Engler, N.; Feldt, M.; Girard, J.; Gratton, R.; Hagelberg, J.; Keller, C.; Keppler, M.; Kenworthy, M.; Kral, Q.; De Breuck, C.; Testi, L.; Immer, K.; Report on the Lopez, B.; Maire, A.-L.; Menard, F.; Mesa, D.; ESO Workshop “Getting Ready for ALMA Band 5 Messina, S.; Meyer, M. R.; Milli, J.; Min, M.; Muller, — Synergy with APEX/SEPIA”; 167, 11 A.; Olofsson, J.; Pawellek, N.; Pinte, C.; Szulagyi, de Zeeuw, T.; Comerón, F.; Tamai, R.; A Long J.; Vigan, A.; Wahhaj, Z.; Waters, R.; Zurlo, A.; Expected Party — The First Stone Ceremony for Three Years of SPHERE: The Latest View of the Extremely Large Telescope; 168, 2 the Morphology and Evolution of Protoplanetary de Zeeuw, T.; Gilmozzi, R.; In Memoriam Giovanni Discs; 169, 32 Bignami; 168, 53

54 The Messenger 171 – March 2018 Gravity Collaboration; First Light for GRAVITY: A L Popescu, M.; Licandro, J.; Morate, D.; de León, J.; New Era for Optical Interferometry; 170, 10 Nedelcu, D. A.; Minor Planet Science with the Grothkopf, U.; Bordelon, D.; Meakins, S.; Emsellem, Leibundgut, B.; Bordelon, D.; Grothkopf, U.; Patat, VISTA Hemisphere Survey; 167, 16 E.; On the Availability of ESO Data Papers on F.; Scientific Return from VLT instruments; 169, 11 Popping, G.; Agnello, A.; Fellows at ESO; 168, 54 arXiv/astro-ph; 170, 58 Leibundgut, B.; Bacon, R.; Jaffé, Y. L.; Johnston, E.; Primas, F.; Guinot, G.; Strandberg, L.; Highlights Guzzo, L.; The Vipers Team; The VIMOS Public Kuntschner, H.; Selman, F.; Valenti, E.; Vernet, J.; from the CERN/ESO/NordForsk “Gender in Extragalactic Redshift Survey (VIPERS): Science Vogt, F.; MUSE WFM AO Science Verification; 170, Physics Day”; 167, 39 Highlights and Final Data Release; 168, 40 20

S H M Smette, A.; Kerber, F.; Kaufer, A.; Report on the Harrison, C.; Swinbank, M.; 1000 High-redshift Mainieri, V.; Popesso, P.; Report on the ESO and “2017 ESO Calibration Workshop: The Second- Galaxies with Spatially-resolved Spectroscopy: Excellence Cluster Universe Workshop “Galaxy Generation VLT Instruments and Friends”; 167, 37 Angular Momentum over 10 Billion Years; 168, 36 Ecosystem: Flow of Baryons through Galaxies”; Spavone, M.; Capaccioli, M.; Napolitano, N. R.; Hofmann, W.; The Cherenkov Telescope Array: 170, 61 Iodice, E.; Grado, A.; Limatola, L.; Cooper, A. P.; Exploring the Very-high-energy Sky from ESO’s Marsset, M.; Carry, B.; Pajuelo, M.; Viikinkoski, M.; Cantiello, M.; Forbes, D. A.; Paolillo, M.; Schipani, Paranal Site; 168, 21 Hanuš, J.; Vernazza, P.; Dumas, C.; Yang, B.; P.; Unveiling the Nature of Giant Ellipticals and Humphreys, L.; Biggs, A.; Immer, K.; Laing, R.; Liu, SPHERE Sheds New Light on the Collisional their Stellar Halos with the VST; 170, 34 H. B.; Marconi, G.; Mroczkowski, T.; Testi, L.; History of Main-belt Asteroids; 169, 29 Spyromilio, J.; Leibundgut, B.; Fransson, C.; Yagoubov, P.; ALMA Band 5 Science Verification; McLure, R.; Pentericci, L.; the VANDELS team; Larsson, J.; Migotto, K.; Girard, J.; Supernova 167, 7 VANDELS: Exploring the Physics of High-redshift 1987A at 30; 167, 26 Husemann, B.; Tremblay, G.; Davis, T.; Busch, G.; Galaxy Evolution; 167, 31 Spyromilio, J.; Dierickx, P.; Jerry Nelson — An McElroy, R.; Neumann, J.; Urrutia, T.; Krumpe, M.; Mérand, A.; Report on the Workshops “VLTI Appreciation of his Pioneering Telescope Work; Scharwächter, J.; Powell, M.; Perez-Torres, M.; Community Days” “VLTI Winter School”; 168, 49 169, 67 The CARS Team; The Close AGN Reference Mérand, A.; Berger, J.-P.; de Wit, W.-J.; Eisenhauer, Stoehr, F.; Manning, A.; Moins, C.; Jenkins, D.; Lacy, Survey (CARS); 169, 42 F.; Haubois, X.; Paumard, T.; Schoeller, M.; M.; Leon, S.; Muller, E.; Nakanishi, K.; Matthews, Hussain, G. A. J.; Message from the Editor; 170, 70 Wittkowski, M.; Woillez, J.; Wolff, B.; GRAVITY B.; Gaudet, S.; Murphy, E.; Ashitagawa, K.; Science Verification; 170, 16 Kawamura, A.; The ALMA Science Archive; 167, 2 Messias, H.; Man, A.; Fellows at ESO; 170, 66 Stoehr, F.; The Deadline Flurry Formula; 169, 53 K Mroczkowski, T.; Stroe, A.; Andreani, P.; Arnaud, M.; Sybilska, A.; De Cia, A.; Lillo Box, J.; Fellows at ESO; Arrigoni Battaia, F.; De Breuck, C.; Sobral, D.; 167, 4 5 Kasper, M.; Arsenault, R.; Käufl, H.-U.; Jakob, G.; Report on the ESO Workshop “Early Stages of Fuenteseca, E.; Riquelme, M.; Siebenmorgen, R.; Galaxy Cluster Formation 2017 (GCF2017)”; 170, Sterzik, M.; Zins, G.; Ageorges, N.; Gutruf, S.; 63 V Reutlinger, A.; Kampf, D.; Absil, O.; Carlomagno, B.; Guyon, O.; Klupar, P.; Mawet, D.; Ruane, G.; Venemans, B. P.; ALMA Observations of z ~ 7 Karlsson, M.; Pantin, E.; Dohlen, K.; NEAR: Low- O Quasar Hosts: Massive Galaxies in Formation; mass Planets in a Cen with VISIR; 169, 16 169, 48 Kervella, P.; Montargès, M.; Richards, A. M. S.; Oteo, I.; External Fellows at ESO; 170, 68 Homan, W.; Decin, L.; Lagadec, E.; Ridgway, S. T.; Perrin, G.; McDonald, I.; Ohnaka, K.; The Nearby Evolved Star L2 Puppis as a Portrait W of the Future Solar System; 167, 20 P Khorrami, Z.; Vakili, F.; Lanz, T.; Langlois, M.; Watson, F.; Couch, W.; Astronomy in Australia; 170, Lagadec, E.; Meyer, M. R.; Gratton, R.; Beuzit, Paladini, C.; Klotz, D.; Sacuto, S.; Lagadec, E.; 2 J.-L.; Mouillet, D.; Towards a Sharper Picture of Wittkowski, M.; Richichi, A.; Hron, J.; Jorissen, A.; R136 with SPHERE Extreme Adaptive Optics; 168, Groenewegen, M. A. T.; Kerschbaum, F.; 32 Verhoelst, T.; Rau, G.; Olofsson, H.; Zhao-Geisler, Kraus, S.; Kluska, J.; Kreplin, A.; Bate, M.; Harries, R.; Matter, A.; To be or not to be Asymmetric? T.; Hofmann, K.-H.; Hone, E.; Monnier, J.; Weigelt, VLTI/MIDI and the Mass-loss Geometry of AGB G.; Anugu, N.; de Wit, W.-J.; Wittkowski, M.; Stars; 168, 28 VLTI Imaging of a High-Mass Protobinary System: Patat, F.; Hussain, G. A. J.; Gadotti, D.; Primas, F.; Unveiling the Dynamical Processes in High-Mass Period 100: The Past, Present and Future of ESO Star Formation; 170, 45 Observing Programmes; 169, 5 Patat, F.; Boffin, H. M. J.; Bordelon, D.; Grothkopf, U.; Meakins, S.; Mieske, S.; Rejkuba, M.; The ESO Survey of Non-Publishing Programmes; 170, 51 Plunkett, A.; Comerón, F.; Testi, L.; Report on the ESO Workshop “Star Formation from Cores to Clusters”; 169, 58 Plunkett, A.; Yen, H. W.; Fellows at ESO; 169, 68 Poggianti, B. M.; Gullieuszik, M.; Moretti, A.; Jaffé, Y. L.; Fritz, J.; Vulcani, B.; Bettoni, D.; Bellhouse, C.; Fasano, G.; Radovich, M.; the GASP collaboration; Tales of Tails: Gas Stripping Phenomena in Galaxies with MUSE; 170, 29

The Messenger 171 – March 2018 55 ESO, the European Southern Observa- Contents tory, is the foremost intergovernmental astronomy organisation in Europe. It Telescopes and Instrumentation is supported by 16 countries: Austria, D’Odorico S. – 40+ Years of Instrumentation for the Belgium, Brazil, the Czech Republic, La Silla Paranal Observatory 2 Denmark, France, Finland, Germany, Hainaut O. R. et al. – End-to-End Operations in the ELT Era 8 Italy, the Netherlands, Poland, Portugal, Mérand A. – The VLTI Roadmap 14 Spain, Sweden, Switzerland and the Cirasuolo M. et al. – The ELT in 2017: The Year of the Primary Mirror 20 United Kingdom. ESO’s programme is focused on the design, construction Astronomical Science and operation of powerful ground- Bastian T. S. et al. – Exploring the Sun with ALMA 25 based observing ­facilities. ESO oper- Cami J. et al. – The ESO Diffuse Interstellar Band Large ates three observatories in Chile: at Exploration Survey­ (EDIBLES) 31 La Silla, at Paranal,­ site of the Very Baudry A. et al. – APEX Band 9 Reveals Vibrationally Excited Large Telescope, and at Llano de Water Sources in Evolved Stars 37 Chajnantor. ESO is the European partner in the Atacama Large Millimeter/sub- Astronomical News millimeter Array (ALMA).­ Currently ESO Benz W. – New President of Council 43 is engaged in the construction of the Roche P. – Review of the Last Three Years at ESO 44 Extremely Large Telescope.­ Andreani P. et al. – Report on the ESO Workshop “QUESO: Submillimetre/ Millimetre/Centimetre Q & U (and V )” 46 The Messenger is published, in hard- Evans C. et al. – Report on the MOSAIC Science Colloquim “Spectroscopic copy and electronic form, four times Surveys with the ELT: A Gigantic Step into the Deep Universe” 47 a year: in March, June, September and Fellows at ESO – Kakkad D., Bartlett E., Lu H.-Y. 49 December. ESO produces and distrib- Personnel Movements 52 utes a wide variety of media connected­ to its activities. For further information, Annual Index 2017 (Nos. 167–170) 53 including postal subscription to The Messenger, contact the ESO education and Public Outreach Department at:

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Unless otherwise indicated, all images in The Messenger are courtesy of ESO, Front cover: ALMA observes gaps in the young except authored contributions which protoplanetary disc AS 209 in the Ophiuchus star are courtesy of the respective authors. forming region. The outer gap is consistent with a giant planet and the inner gap may indicate © ESO 2018 a smaller planet closer to the central star. ISSN 0722-6691 Credit: ALMA (ESO/NAOJ/NRAO)/D. Fedele et al.