The Messenger

No. 132 – June 2008 10th anniversary of VLT First Light First VLT anniversary of 10th Paranal on seeing layer ground The Verification Science HAWK-I Antares around nebula emission The The Organisation

The Perfect Machine

Tim de Zeeuw a ground-based spectroscopic comple­ thousand each semester, 800 of which (ESO Director General) ment to the Hubble Space Telescope. are for Paranal. The User Portal has Italy and Switzerland had joined ESO in about 4 000 registered users and 1981, enabling the construction of the the archive contains 74 TB of data and This issue of the Messenger marks the 3.5-m New Technology Telescope with advanced data products. tenth anniversary of first light of the Very pioneering advances in active optics, Large Telescope. It is an excellent occa­ ­crucial for the next step: the construction sion to look at the broader implications of the Very Large Telescope, which Winning strategy of the VLT’s success and to consider the received the green light from Council in next steps. 1987 and was built on Cerro Paranal in The VLT opened for business some five the Atacama desert between Antofagasta years after the Keck telescopes, but the and Taltal in Northern Chile. The 8.1-m decision to take the time to build a fully Mission Gemini telescopes and the 8.3-m Subaru integrated system, consisting of four telescope were constructed on a similar 8.2-m telescopes and providing a dozen ESO’s mission is to enable scientific dis­ time scale, while the Large Binocular Tele­ - foci for a carefully thought-out comple­ coveries by constructing and operating scope and the Gran Telescopio Canarias ment of instruments together with four powerful observational facilities that are now starting operations. 1.8-m Auxiliary Telescopes for the inter­ are beyond the capabilities of individual ferometer, was the right one. The combi­ member states. This principle was under­ The VLT was designed from the start as nation of a long-term adequately-funded stood right at the start in 1962, when an integrated system of four 8.2-m tele­ instrument and technology development ­Belgium, France, Germany, Sweden and scopes, including the possibility to com­ plan, with an approach where most of the Netherlands created ESO (with bine the light from individual telescopes the instruments were built in collaboration ­Denmark joining in 1967) to build a large for optical interferometry, enabling stu­ with institutions in the member states, telescope in the South. The main moti­ pendous spatial resolution. First light on with in-kind contributions in labour com­ vation was the need to be able to com­ Antu occurred in May 1998, with Kueyen, pensated by guaranteed observing time, pete scientifically with astronomers in Melipal and Yepun following soon after. has created the most advanced ground- California who had access to large private Most of the VLT and VLTI instruments based optical observatory in the world. telescopes, most notably the 5-m Hale were built in close collaboration with insti­ The operations model distinguishes visi­ telescope on Mount Palomar, known as tutes in the member states. The entire tor and service mode, and provides the ‘Big Eye’, and considered by many first-generation instrument suite was com- world-leading observing efficiency on a to be ‘The Perfect Machine’ of its time. In pleted in 2007 with the commissioning site where nearly 90 % of the nights are the United States of America, the same of CRIRES. The Paranal arsenal includes clear. All of this was made possible by the motivation had already led in 1957 to the turnkey adaptive optics systems and motivation of ESO staff members to build, creation of AURA, the Association of a rapid-response mode to react to fast operate and support the best possible ­Universities for Research in Astronomy, transient events. Recently, the near-­ observatory. As a result, the VLT is argua­ which resulted in the Kitt Peak and Cerro infrared imager HAWK-I was added as a bly the natural successor of the ‘Perfect Tololo Observatories, each including a ‘generation-1.5’ instrument. Machine’ on Mount Palomar. Our 2007 4-m telescope and supported by the Visiting Committee, chaired by Professor National Science Foundation. In Europe The VLT and VLTI have contributed to all Günther Hasinger, stated it thus: “ESO the ESO mission resulted in the con­ areas of astronomy, including the nature has become the premier observatory for struction of the La Silla Observatory north of dark matter and dark energy, the ex- optical-infrared astronomy on a world- of La Serena in Chile, operating a fleet treme physics of gamma-ray bursts and wide basis.” of telescopes, with the 3.6-m as flagship. supernovae, the formation, structure and evolution of galaxies, the properties The stunning scientific success of the VLT of super-massive black holes in galactic attracted new member states to ESO. The Very Large Telescope ­nuclei, in particular the one in the Galac­ In the past decade Portugal joined (after tic Centre, of star clusters and stellar a ten-year associate status), followed by By the early 1980’s there were half-a- populations, of the interstellar and inter- the United Kingdom, Finland, Spain and dozen observatories with 4-m-class tele­ galactic medium, the formation of stars the Czech Republic. At the time of writ- scopes available to astronomers world- and planets, the properties of exo- ing it looks likely that Austria will join later wide, La Silla being one of them. Plans planets, and of Solar System objects. The this year (see text of Press Release on were being drawn-up to construct much output in terms of refereed research page 5). These countries are drawn to more powerful telescopes with ­primary papers was 469 in 2007 alone, bring- ESO because of the unique observing mirrors in the 8–10-m range. The Keck ing the total since first light to over 2 200, opportunities and by the possibility to be Foundation enabled the California Insti­ with the annual rate still increasing. involved in a coherent long-term pro­ tute of Technology and the University of gramme involving the design, construc­ California to build twin 10-m telescopes The total number of observing proposals tion and operation of future world-class on Mauna Kea, obtaining first light in for ESO facilities has doubled in the past ground-based facilities for astronomy. the early nineties, providing, in particular, decade, and now approaches nearly a As their annual contribution and entrance

2 The Messenger 132 – June 2008 The VLT as it is today with four Unit Telescopes and four Auxiliary Tele­ scopes. Photo: H. H. Heyer, ESO

fee is added to ESO’s income, the acces­ 5 050-m altitude on Chajnantor east of ence exploitation, building on expertise sion of new member states also enables San Pedro de Atacama in northern Chile. with existing sub-millimetre telescopes, new projects. ALMA evolved from separate regional including APEX, and on science to plans to a global partnership between be done with the 3.5-m Herschel Space Europe, North America (USA and Can­ Obser­vatory, which ESA expects to The next steps ada) and East Asia (Japan and Taiwan), launch in 2009. with ESO representing Europe. Partici­ The VLT will continue to increase in pation in ALMA expands ESO’s activities The next world-class ground-based facil­ power over the next decade. X-Shooter into a wavelength regime often associ­ ity is the European Extremely Large will come on line this year, with KMOS, ated with radio astronomy. The first step Telescope for the visible/infrared wave­ SPHERE and MUSE to follow, together has already been taken: ESO operates length regime. ESO is undertaking the with multiple laser guide stars, an adap­ APEX, a single-dish 12-m antenna for sub- design study, in close collaboration with tive secondary mirror on Yepun, and millimetre astronomy located on Chajnan­ industry and institutes in the member one or more third-generation instruments, tor, in a partnership with Sweden and the states. The baseline design consists of a including an ultra-stable high-resolution Max-Planck-Gesellschaft. 42-m ­segmented primary mirror, an inno­ spectrograph at the combined focus vative five-mirror design, and adaptive (as foreseen in the original VLT design). ALMA construction is well underway. optics built into the telescope. The study The VLTI will be equipped with the sec­ ESO has delivered key components, draws on the entire expertise built up in ond-generation instruments GRAVITY including the Technical Building for the ESO and the member states over the and MATISSE, to be followed by VSI, the Observing Support Facility at 2 950 m, past decades, including lessons learned latter perhaps with two additional Auxil­ and two antenna transporters (see the from ALMA construction. The aim is to iary ­Telescopes, if external funding can article on page 23). Institutes in the be ready for a construction start in 2010, be found. ­member states are providing the Band 7 so that there is an opportunity for over- and Band 9 high-frequency receivers lap with the James Webb Space Tele­ VISTA and the VST are expected to start and front-end integration for the 66 ALMA scope, which is the next NASA/ESA/CSA regular operations next year with a five- antennas. The 25 12-m antennas to be flagship facility. year programme of coherent public sur­ delivered by European industry are be- veys led by international teams. These hind schedule, with the first one arriving This combined programme is ambitious, surveys are performed together with data in Chile in the first half of 2009, where but achievable by building on the ‘VLT centres in the member states, coordi­ Japan and North America already have model’ in which high-quality staff carries nated by ESO. This collaboration builds a four antennas each at the OSF being out a coherent programme in close European survey capability which will readied for acceptance. The hope is that ­collaboration with scientists and institu­ deliver eminent science, provides ­crucial the schedule slip can be recovered tions in the member states, with long- ground-based data in support of future through a speedy delivery of the later term planning enabled by the security of space missions, and prepares the way for antennas. The creation of the ALMA an intergovernmental treaty. the next step in surveys. ­European Regional Centre, with nodes in many of the member states, will help ESO continues to attract and train high- The Atacama Large Millimeter/submilli­ ­prepare the European astronomical com­ quality staff both in Chile and in Garching. meter Array is being constructed at munity for leadership in ALMA sci- In the past eight months I spent a fair

The Messenger 132 – June 2008 3 The Organisation

amount of time at our sites in Chile, and crucial for ESO’s ability to deliver the best When the VLT turns 15 in five years time, after each visit I came away impressed by observing facilities for the member states. the medium-sized telescopes on La Silla the dedication and motivation of our per­ will be focused on unique long-term sci­ sonnel in all areas of expertise. The same ESO’s Fellowship programme deserves ence, the VLT and VLTI will be nearing is true for our staff members in Garching, special mention. It also has grown over their full potential, and ALMA will be oper­ who provide general user support, de- the past decade. A remarkable statistic is ational. If all goes well, the Extremely velop critical software, coordinate the that 92 % of all former ESO Fellows are Large Telescope will be in construction, construction of new instrumentation, and still active in astronomy, many in institu­ and ESO and the member states will al- follow developments in technology (both tions in the member states. This strength­ ready be planning for another world-class of which include in-house activities). The ens the partnership between ESO and ground-based facility. This entire pros­ astronomers have a fraction of their time the member states in a natural way, con­ pect is very exciting and I look forward to available for personal research, as this is tributing to the long-term success of the being a part of this. entire programme.

10th Anniversary of First Light of the VLT

On 16 May 1998, ‘First Light’, in the sense VLT UT1 First Light of imaging with active optics and tele­ image of Omega ­Centauri. scope tracking, was obtained with the VLT Test Camera for Unit Telescope 1. The First Light image, which originally ap- peared in The Messenger, No. 92 is reproduced here and shows a 10-min R-band image of the globular cluster Omega Centauri. The image was actually obtained before the mirror was coated but has measured image quality (Full Width at Half Maximum) of 0.43 arcsec. The accompanying photograph taken during that period shows the three key staff – Massimo Tarenghi, then director of the Paranal Observatory, Roberto Gil­ mozzi and Jason Spyromilio – in the VLT control room. All three are still with ESO: ­Massimo has been ALMA Director, ­Roberto succeeded Massimo as director of the Paranal Observatory and was ­himself succeeded by Jason. Both are now working on ESO’s next large tele­ scope project – the European Extremely Large Telescope (E-ELT). The understa- Massimo Tarenghi, ted sense of jubilation at the meeting of ­Roberto Gilmozzi and Jason Spyromilio in performance criteria is well caught in the the VLT control room in quotation from the article “The First Steps May 1998. of UT1” by Tarenghi, Gray, Spyromilio and Gilmozzi, which appeared in The Messenger No. 93, printed here.

To mark this anniversary a poster has been produced by the ESO Public Affairs Department (PAD) group and is enclosed with this issue.

4 The Messenger 132 – June 2008 “Although first light was specified for the low wind and good seeing. We started a peared at 0.48 arcseconds. A series of night of the 25th of May, the internal plan- 10-minute exposure on target with the other measurements on tracking stabil- ning target date was the 15th of May. test camera. We had never tried anything ity and image quality verified the tele- By this time we had moved out of the hut as long as this. Krister Wirenstrand scope had met all the performance crite- in the enclosure and were operating the ­anxiously waited for the test camera CCD ria for first light.” tele­scope from the relative comfort of the to read out. This was to be the first true control room. On the night of the 15th of image taken with the telescope on a Tarenghi, M., Gray, P., Spyromilio, J. & Gilmozzi, R. May we decided that we should meet all scientific CCD. When the image was 1998, The Messenger, 93, 4 specifications laid out in the integration transferred to the Real Time Display, we plan for the telescope. The target was to quickly measured the image quality. be w Cen. Conditions were excellent: Great jubilation again as the stars ap-

Austria Declares Intent to Join ESO

At a press conference held at the Uni­ versity of Vienna Observatory on 24 April 2008, the Austrian Science Minister Johannes Hahn announced the decision by the Austrian Government to seek membership of ESO from 1 July of this year.

Said Minister Hahn: “With membership of ESO, Austria’s scientists will receive ­direct access to the world’s leading infra­ structure in astronomy. This strengthens Austria as a place for research and pro­ vides an opportunity for young research­ ers to continue their work from here. With this move, Austria takes an important step in the reinforcement of Europe’s sci­ ence and research infrastructure.”

The ESO Director General Tim de Zeeuw responded: “ESO welcomes the Austrian bid to join our organisation. I salute the Austrian Government for taking this im- portant step and look forward to working closely with our Austrian friends and col­ All these projects require some of the From left to right: Prof. Tim de Zeeuw, ESO Director leagues in the years to come.” most advanced technologies in key areas General, Prof. Sabine Schindler, the President of the Austrian Society for Astronomy and Astrophysics, such as optics, detectors, lightweight and Dr. Johannes Hahn, the Austrian Science Minis­ The decision constitutes a major break­ structures, etc. Austrian participation in ter. through for Austrian astronomers who ESO opens the door for Austrian industry have argued for joining ESO for many and major research institutes to take interest in contributing to the devel­ years. Membership would mean not only part in the development of such technol­ opment of the advanced technologies unrestricted access to ESO’s world-­ ogies, with their associated potential for required for ESO’s future projects. leading observational facilities, including industrial spin off. the Very Large Telescope and full partic­ The Austrian bid for ESO membership ipation in the international ALMA project, The main centres for astronomical was formally approved by the ESO Coun­ but also the possibility to participate in research in Austria are at the Universities cil at its meeting on 3–4 June and is now future projects, including the realisation of Graz, Innsbruck and Vienna. Further- subject to ratification by the Austrian Par­ of the European Extremely Large Tele­ more, scientists in the area of mathe­ liament. scope (E-ELT), which is currently in its matics, applied physics and computer design phase. science have already expressed their (Adapted from ESO Press Release 11/08)

The Messenger 132 – June 2008 5 Telescopes and Instrumentation VISTA on VISTA on 2008. 16 April in installed being mirror primary 4.1-m f/1 The Telescopes and Instrumentation

Hawk-I – First Results from Science Verification

Markus Kissler-Patig1 of the instrument. Here we briefly de- were obtained, for a grand total of 27 Andrea Fontana 2 scribe a selection among the twelve ac- hours of integration. The final mosaic pro­ Bram Venemans 3 cepted Science Verification programmes vides the deepest image ever obtained Jean-Paul Kneib 4 and highlight some of the first spectac­ in the Y-band. Thanks also to the excel­ Michelle Doherty1 ular results in the areas of distant galax­ lent image quality (< 0.5?), it enables the Christopher Lidman1 ies, clusters of galaxies, star clusters and detection of galaxies as faint as m(AB) Harald Kuntschner 5 star formation. = 26.8. The preliminary photometric anal­ Mark Norris 6 ysis has identified a set of 25 high-red­ Soeren Larsen7 The science verification (SV) for HAWK-I shift candidates. Extensive simulations Mark Gieles1 was interleaved with the commissioning are underway to assess the complete­ Alcione Mora Fernandes 8 activities that took place in three runs ness and reliability of the selected sam­ Mark McCaughrean 9 between October 2007 and February ple. Thomas Preibisch10 2008. The goal of SV was to demonstrate Andreas Seifahrt11 the capabilities of the new instrument This programme was complemented by Jon Willis12 in a wide variety of research fields. More HAWK-I observations in the NB1060 filter Elizabeth Wehner13 details on SV, the selected programmes as an alternative method to search for and all the data, together with a de- star-forming galaxies at z = 7.7, thus dem­ scription of how they were acquired, can onstrating the potential of HAWK-I in di- 1 ESO be found on the HAWK-I SV web pages rectly probing the epoch of re-ionisation. 2 INAF – Osservatorio Astronomico di (http://www.eso.org/sci/activities/vltsv/ The SV observations alone will form a Roma, Italy hawkisv/). HAWK-I was offered to the sufficiently complete dataset to put a con- 3 Institute of Astronomy, University of community in Period 81 for regular serv­ straint on the number of luminous star- Cambridge, United Kingdom ice and visitor mode observing. forming galaxies at z = 7.7. Preliminary 4 OAMP, Laboratoire d’Astrophysique de analysis of 8.3 hours of narrowband data Marseille, France indicates that HAWK-I is capable of 5 ST-ECF, ESO Distant galaxies reaching a limiting depth of 7.5 × 10–18 erg 6 Department of Physics, University of s–1 cm–2 arcsec–2 (5 sigma). By measur- Durham, United Kingdom HAWK-I observations in the GOODS-S ing the colours of the candidate line emit­ 7 Astronomical Institute, University of field were designed to obtain a self-con­ ters in the available HST/ACS images of Utrecht, the Netherlands sistent sample of galaxies at redshift the field, the line which has caused the 8 Departamento de Física Teórica C-XI, about 7, providing a new view on the Uni­ narrowband excess can be determined. Universidad Autónoma de Madrid, verse at the end of the epoch of re-ioni­ Figure 1 shows a colour-magnitude dia­ Spain sation. The extraordinary efficiency of gram of detected sources and an exam­ 9 School of Physics, University of Exeter, HAWK-I was used to detect z > 6.5 can­ ple image of a low-redshift emission-line United Kingdom didates in the Y-filter (centred at 1.021 μm) galaxy. 10 Max-Planck-Institut für Radioastro­ through an appropriate recasting of nomie, Bonn, Germany the Lyman-break technique: candidates A programme with similar aims, but using 11 Institut für Astrophysik, Georg-August- are selected as “Z-drop”, i.e. their col- a different technique, aimed at detecting Universität, Göttingen, Germany ours satisfy the following criteria: (Z–Y) > high-redshift (z ~ 7.7) Ly-a emitters am- 12 Department of Physics and Astronomy, 1.0 mag. and (Y–K) < 1.5 mag. 333 frames plified by the strong lensing of a massive University of Victoria, Canada 13 Department of Physics and Astronomy, McMaster University, Hamilton, Canada B VI Z Sigma = 3 2

The VLT wide-field near-infrared imager 40 HAWK-I was commissioned in 2007 and Zphot = 0.69 –> L(Hα) = 8 × 10 erg/s Science Verification (SV) programmes 1 were conducted in August 2007. A selec- Equivalent Width = 100 A Figure 1. Colour-magni­ tude diagram showing tion of results from among the twelve objects detected in one Science Verfication proposals are sum- of the four HAWK-I 0 chips. ­Candidate emis­ marised. Y – NB1060 (AB) sion-line galaxies are objects with a significant flux excess in the nar­ HAWK-I is the new wide-field infrared im- row-band filter. The inset ager on the VLT. We reported previously –1 shows ACS ­images of in The Messenger on its capabilities an example low-redshift line emitter, detected (Casali et al., 2005) and refer to Kissler- 14 16 18 20 22 24 26 through Ha redshifted to Patig et al. (2008) for a recent description NB1060 magnitude (AB) z = 0.69.

The Messenger 132 – June 2008 7 Telescopes and Instrumentation Kissler-Patig M. et al., Hawk-I – First Results from Science Verification

cluster. The massive cluster MS0451-03 Figure 2. A ~ 2.5; × 2; section of a was observed with the NB1060 filter of HAWK-I Ks-band image contain- ing the radio galaxy MRC0030-219, HAWK-I. The magnification of background which is marked with an arrow. galaxies ranges from 0.3 to 3 mag. The NB image provides an effective test for the presence of gravitationally lensed z ~ 7.7 galaxies. Many interloping z < 7 galaxies are detected in this image and will be of wider interest for follow-up studies.

Galaxy clusters

There is now strong evidence that galaxy evolution is closely linked to environment Figure 3. Colour composite of four and that the oldest, reddest galaxies lo- HAWK-I pointings in both J and Ks, covering 13.5; on a side, of the gal- cally are found in large clusters. Hence to axy cluster XMMU J2235.3-2557. The study the early stages of galaxy evolution ­cluster is in the middle of the frame we need to study the highest redshift and a blow-up centred on the cluster (proto-)clusters. The number of these cur­ is shown in the inset. The centre of XMMU J2235.3-2557 is dominated by rently known is small but one of the most red galaxies with very similar colours. promising ways to locate them is by char­ acterising the environment of high-red­ shift radio galaxies which lie at the cen­ tres of proto-clusters. HAWK-I was used to image the radio galaxy MRC0030-219 at z = 2.168 in the J-, K- and NB1190-fil­ ters (see Figure 2 for the K-band image). At this redshift the narrowband filter traces [O ii] 3727 Å emission: the aim is to search for an overdensity of star-forming galaxies and at the same time for redder, evolved galaxies using J–K colours. Initial ages, the image quality reached 0.2?, ing. Overplotted are Maraston et al. analysis seems to indicate no evidence which approaches that obtainable with (2003) SSP models for ages 3–15 Gyr for an over-density but this is still to be NICMOS on HST, but with the advantage and [Z/H] –2.25 to 0.67. The depth of the verified. If true, it will allow interesting lim­ of a much larger field of view. HAWK-I data allows exploration of the its to be placed on the properties of a interesting blue end (intermediate ages?) radio galaxy required for a forming proto- of the colour distribution in V–Ks. cluster. Star clusters In a similar programme HAWK-I was used A ubiquitous feature in rich galaxy clus­ Globular clusters provide important tools to study the star cluster system of the ters at all redshifts is the tight sequence to distinguish between competing models intermediate-age (~ 3 Gyr) merger rem­ of red, passively-evolving early-type gal­ for the formation of their host galaxies. nant NGC 1316. This galaxy has a sub­ axies in the colour-magnitude diagram. The combination of optical and IR pho­ stantial number of star clusters, some of HAWK-I is well suited for studying the for­ tometry is a very powerful tool to investi­ which have ages corresponding to the mation of the red sequence and of rich gate the age distribution of globular clus­ merger. However, it is not clear what frac­ galaxy clusters in general, since such ters in a given system. However, currently tion were formed during this most recent clusters form over regions that are several available samples are severely limited by merger event. The new, deep Ks-band Mpc in size. In the concordance cosmol­ the spatial coverage of the IR data. With imaging (Figure 5) has already revealed ogy, 5 Mpc corresponds to 10; on the HAWK-I, wide field J-, H-, Ks-band imag­ an extensive system of star clusters and, sky at a redshift of 1.5. The aim of this SV ing was obtained of the nearest S0 gal­ along with archival VIMOS optical imag­ programme was to image the galaxy axy NGC 3115. A preliminary colour-col­ ing and spectroscopy, will allow the var­ cluster XMMU J2235.3-2557 at z = 1.39, our plot, obtained using archival FORS2 ious cluster populations in NGC 1316 to one of the most distant X-ray luminous imaging and the HAWK-I SV data (filled be clearly separated and their ages and clusters known. The resulting images black circles), is shown in Figure 4, and metallicities to be constrained. were superb (see Figure 3). In Ks, the compared with previous measurements image quality of the final stack reached (open blue circles) by Puzia et al. (2002) The spiral galaxy NGC 7793 was also 0.32?, and, in some of the individual im- who used ISAAC and HST/WFPC2 imag­ observed with HAWK-I to complement

8 The Messenger 132 – June 2008 30 Figure 4. V–I versus tions are surprising, NGC 602 was ob- 25 V–Ks colour-colour dia­ served with HAWK-I, taking advantage of gram, with associated 20 its high spatial resolution and sensitivity,

N projections of the axes, 15 of globular clusters in order to analyse the association of 10 in NGC 3115. The black 5 IRAC protostars and their suggested opti­ points refer to data cal counterparts. Figure 6 shows the taken with FORS2 and 1.4 1.4 HAWK-I, the blue points spectacular HAWK-I composite JHKs to data from HST WF/ image of the young stellar population and PC2 and ISAAC. 1.3 1.3 the nebulosity in NGC 602/N 90. The 0.5–8 μm SED was computed, using the 1.2 1.2 preliminary HAWK-I fluxes, of three previ­ ously suggested Class I protostellar objects in the region (see Figure 7). It is

(Mag) 1.1 1.1 apparent that the near-IR data are essen­

V–I tial to determine the true nature of these 1.0 1.0 objects.

0.9 0.9 High spatial resolution H2 2.122 micron images of the highly symmetric proto- 0.8 0.8 stellar jet HH 212 were made with HAWK‑I. Since the jet fits within a single quadrant 1 234 5 10 15 20 V–Ks (Mag) N of the HAWK-I field of view, these data provide a stable, precision astrometric Star formation template to which the archival mosaiced ISAAC images of HH 212, taken from NGC 602/N 90 in the Small Magellanic 2001–2006, can be aligned. The scientific Cloud (SMC) hosts a cluster of Young aim is to measure transverse motions Stellar Objects (YSOs) including pre- in the outflow down to 20 km/s to trace main-sequence (PMS) stars detected by the dynamical history of the jet and thus HST/ACS and Class 0-I protostars de- the accretion history of the underlying tected by Spitzer/IRAC. Some protostel- protostar. The HAWK-I observations lar objects are apparently related to op­- also extend the proper-motion monitor- tical PMS stars. Since the Spitzer/IRAC ing baseline from five to seven years, beam is relatively large and such associa­ ­further improving the velocity resolution.

Figure 5. A deep HAWK-I Ks-band image of NGC 1316 showing many star clusters. The inter- chip gaps are apparent on this combined image. existing wide-field optical HST/ACS data and to study its star cluster population. The combination of NIR and optical data and the large field of view of HAWK-I allow construction of the cluster luminos­ ity function, the cluster initial mass func­ tion and the cluster age distribution of the entire cluster population, and for dif­ ferent environments within the disc. This Figure 6. JHKs colour will shed light into how cluster masses composite of the central depend on the star formation rate of the region of NGC 602/N90. Reflection nebulae and host galaxy and how the early disrup- a rich stellar population, tion due to the removal of natal gas, or mainly grouped in clus­ ‘infant mortality’ of clusters, depends on ters, are distinguished, local variables. together with many background galaxies.

The Messenger 132 – June 2008 9 Telescopes and Instrumentation Kissler-Patig M. et al., Hawk-I – First Results from Science Verification

A deep wide-field near-IR survey of the Figure 8). Given the typical proper mo- ing forward to seeing many more spec­ Carina Nebula was performed with tions of Chamaeleon members, a second tacular HAWK-I results reported in the HAWK-I, in order to study the physics of epoch after three years will reveal all Messenger and elsewhere. violent massive star formation and the members of this region down to the free- resulting feedback effects, including cloud floating planetary mass objects (plane- dispersal and triggered star formation. mos) regime. The astrometric perform­ Acknowledgements The survey reveals all young stars in ance is further backed up by the high Many thanks to the SV team who enabled all these the region through extinction of up to AV number of background galaxies identified first science results: Nancy Ageorges, Mark Casali, < 25 mag and brown dwarfs down to in the deep HAWK-I frames. These galax­ Yves Jung, Jorge Melnick, Alan Moorwood, Monika 35 Jupiter masses through 10 mag of ies form the astrometric reference frame Petr-Gotzens, John Pritchard and Masayuki Tanaka. extinction. In combination with recent of the planned second epoch. The cur­ observations at other wavelengths, the rent data of this programme will be made References survey will allow mass, age, and circum­ accessible as an Advanced Data Prod­ stellar disc fraction distributions to be uct. Casali, M., Piraud, J.-F., Kissler-Patig, M., et al. 2005, ascertained for the entire young stellar The Messenger, 119, 6 Kissler-Patig, M., et al. 2008, A&A, accepted population as a function of environment Maraston, C., et al. 2003, A&A, 400, 823 within the Carina Nebula. Prospects Puzia, T. H., et al. 2002, A&A, 391, 453

Deep HAWK-I images (5 sigma K-band HAWK-I is currently the most performant limit approx. 19.5 mag in 12-min on-sky) near-infrared imager on an 8-m-class were collected in two sub-fields of the ­telescope. It has proven its very high Chamaeleon I star-forming region. The throughput and exceptional image quality observations are complete down to at during the SV observations. In period 81, least 5 Jupiter masses, according to the­ HAWK-I has been scheduled for 21 runs oretical isochrones for the typical dis­ and will, without doubt, deliver further tance and age of Chamaeleon I. The in- stunning images. Given its performance, ternal astrometric precision is better than it is on the path to becoming a work- 25 mas (root-mean-squared error – see horse instrument at the VLT. We are look­

10 –15 ACSHAWK-IIRAC 0.2

10 –16 ) 2 0.1 (W/m

λ –17 F

10 ) λ � 0.0 ∆Axis 1 ( 10 –18 –0.1 110 Wavelength (µm)

Figure 7. Spectral energy distribution for selected objects identified as pro­ –0.2 tostars in Spitzer/IRAC images of NGC 602/N 90 having tentative optical counterparts observed with HST/ACS. 0.2 0.1 0.0 –0.1 –0.2 ∆Axis 2 (�)

Figure 8. The X and Y astrometric errors corresponding to the HAWK-I astrometry in the Chamaeleon I star- forming region.

10 The Messenger 132 – June 2008 Telescopes and Instrumentation

Seeing is Believing: New Facts about the Evolution of Seeing on Paranal

Marc Sarazin1 the test camera during the commission­ ­sensitive instruments in the context of the Jorge Melnick1 ing of UT2 revealed an alarming discrep­ ELT site testing campaign, that we have Julio Navarrete1 ancy between the UT2 image quality and finally been able to draw a coherent pic­ Gianluca Lombardi1,2,3 the DIMM seeing, with an average DIMM ture. This article tells the story of the see­ –UT2 difference of ~ 0.2?. During these ing on Paranal. tests that lasted several nights, UT2 was 1 ESO pointing at the same region of the sky 2 National Institute for Astrophysics, and through the same filter as the DIMM, New data ­Bologna Astronomical Observatory, Italy so there was no straightforward explana­ 3 Department of Astronomy, University tion for the lack of agreement. A dramatic FORS2 imaging data of Bologna, Italy manifestation of the discrepancy between the DIMM and the UT’s is given by the A wealth of data has accumulated since time evolution of seeing on Paranal. Fig­ the commissioning of UT2. For example, Since the commissioning of the VLT it ure 1, shows in the left panel, a plot of the the Quality Control process (QC) sys­ has been known that the image quality evolution of DIMM seeing since 1989 tematically logs delivered image quality delivered by the telescopes is better, taken from the ESO astro-climatology from several instruments together with and often much better, than predicted web pages (http://www.eso.org/astclim/ environmental parameters such as wind by the seeing monitor. The advent of paranal/seeing/). The DIMM seeing has speed and direction, air temperature, new sensitive instruments to measure degraded considerably over the past ­telescope position, and DIMM seeing. the optical turbulence profile of the 17 years from a median value of 0.65? in The most complete dataset for image atmosphere over Paranal has finally 1990 to more than 1.1? in 2007. On the quality is the one for FORS2, which will allowed us to understand the origin of other hand, the right panel of Figure 1 be used here. Figure 2 shows the relation this discrepancy: the presence of a shows that the image quality delivered between DIMM seeing and UT2 image highly turbulent layer so close to the by FORS2 and ISAAC seem to have im- quality measured during regular FORS2 ground that it is seen by the seeing proved with time, at least since the in­- operations. The FORS2 data has been monitor, but not by the VLT unit tele- strument values have been systematically corrected for wavelength and airmass scopes. In this article we tell the story logged through the quality control proc­ using the standard formulae based on an of this elusive surface layer. ess! This result could however be a se- infinite outer scale assumption. Only lection effect since some of the PI’s images taken at airmasses less than 1.5 requested special seeing conditions. We and exposure times between 30 s and The inconvenient discrepancy note in passing that the La Silla see- 300 s were used. The FORS2 measure­ ing has also slightly degraded in a similar ments are automatically obtained using It has been known since the commission­ period (http://www.eso.org/astclim/ many objects on each frame, but only ing of the VLT that the image quality de- paranal/seeing/). livered by the UT’s is at times significantly better than the seeing measured by the We have been puzzling for a long time Figure 1. Left: Evolution of DIMM seeing on Paranal Differential Image Motion Monitor (DIMM). about the origin of this rather inconven- since 1989. Right: Evolution of the FORS2 image quality in the R-band and of ISAAC image quality in The difference is not subtle. Already in ient discrepancy, but it has not been until the K-band since January 2002 (MJD = 52 275). The 1999 the careful observations made with recently, with the deployment of new big squares show the averages over 2-month bins.

2

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The Messenger 132 – June 2008 11 Telescopes and Instrumentation Sarazin M. et al., New Facts about the Evolution of Seeing on Paranal

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0 0.5 1 1.5 00.5 11.5 2 Seeing FORS2 (arcsec) Seeing (arcsec) values for which the image quality disper­ seeing. While this has its shortcomings, Figure 2. Relation between DIMM seeing and image sion is less than 0.1? rms have been re- it seems to be sufficiently accurate for OB quality measured by FORS2 between 2004 and 2006. In the left plot is shown a point plot, and the tained. validation purposes. The possibility of dashed line indicates DIMM = FORS2 seeing. In systematically using the sizes of the (Cas­ the right plot, the measurements are shown as histo­ The correlation between DIMM and segrain) Shack-Hartmann (SH) spots of grams of the seeing values for both instruments. FORS2 reproduces the trend observed the active optics system of the UT’s has with the test camera during the commis­ been investigated in this context by two profiles of the atmosphere at each site. sioning of UT2. The mean DIMM seeing of the authors (Julio Navarrete and Marc The most direct way of doing this is to fly is 0.81? while the mean FORS2 image Sarazin). This has the advantage that balloons equipped with very sensitive quality is 0.65?, so on average the DIMM the sizes are routinely logged by the tele­ sensors that can measure the tempera­ overpredicts image quality by about scope control software and therefore ture and wind speed fluctuations as a 0.16 ?, similar to the value of ~ 0.2? meas­ could provide a readily available real-time function of altitude. Of course these ex- ured with the test camera. It may be estimate of the image quality. Figure 3 periments are costly and cannot provide tempting to apply a rule-of-thumb correc­ shows, in the left panel, a comparison real-time diagnostics of the conditions tion of ~ 0.15? to go from DIMM seeing between the image quality measured by on a given night. Thus, a number of tech­ to UT image quality (at similar airmass FORS2 and the SH for about 750 simul­ niques have been developed to do the and wavelength), but one should notice taneous observations between 2002 and job from the ground. The Multi-Aperture that for very good seeing conditions the 2007 (blue dots). The Shack-Hartmann Scintillation Sensor (MASS) is a compact DIMM seeing may be better than the data were corrected by the aberrations of single-star instrument that measures FORS2 image quality, while under very the SH lenslet array (0.35?) measured on scintillation on four concentric zones of bad conditions, the DIMM may indicate a an internal reference source (green dots). the telescope pupil using photomulti- seeing more than 1? worse than FORS2. The right panel shows the corresponding pliers (Kornilov et al., 2003). A statistical So it is important to understand the origin histograms. The median image quality analysis of these signals measures the 2 of the discrepancy between DIMM seeing measured by FORS2 is 0.64?, and 0.63? vertical profile of turbulence Cn (h) in six and UT image quality. by the (corrected) SH spots; both histo­ layers at 0.5, 1, 2, 4, 8, and 16 km above grams are seen to coincide very nicely. the telescope. A MASS unit developed The figure shows that indeed the (aberra­ at the Sternberg Institute (Moscow) under Active optics Shack-Hartmann data tion-corrected) size of the SH spots pro­ joint ESO-CTIO funding observed con­ vides an excellent proxy for image quality. tinuously on Paranal between 2004 and Real-time quality control of service-mode Using the SH information we now have June 2007. In addition to its low-altitude data at the observatory requires a reliable access to a much larger dataset to com­ resolution (about half the layer altitude, way of assessing whether the data com­ pare DIMM seeing with UT image quality. i.e. ± 250 m at 500 m and ± 8 km at plies with the seeing requirements set 16 km), a distinct disadvantage of MASS by the PI’s. While this is straightforward is that it is blind to turbulence close to 2 for imaging data, it is not so for spectros­ Atmospheric turbulence profiles – Cn (h) the ground (the ground layer), which pro­ copy. Thus, the observatory operations duces little scintillation. We will show staff typically rely on the FWHM of the Modern site characterisation campaigns below, however, that for the purpose of stars in the guide probes to estimate the aim at determining the vertical turbulence understanding the discrepancy between

12 The Messenger 132 – June 2008 1.5 150

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DIMM and UT’s, this turns out to be an cant fraction of the seeing over Paranal is Figure 3. Left: Relation between the image quality important advantage. produced by a turbulent layer located delivered by UT1 estimated using the Shack-Hart­ mann (SH) spots of the active optics sensor, and the well below 500 m from the ground. This is value determined on long (30 s–300 s) exposures something that was already known from with FORS2 in the R-band. The data have been nor­ The ground layer previous experiments involving micro­ malised to airmass 1.0 and 500 nm wavelength. thermal sensors on a mast (Martin et al., The blue points are the original SH data, and the green points show the values corrected for a lenslet A straightforward application of the 2000). What is new is that we have a aberration of 0.35?. The dotted line corresponds MASS data is to integrate the profiles to ­substantial body of simultaneous obser­ to FORS2 = SH. Right: Measurements presented as measure the seeing. This is shown in vations which we can use to quantify histograms for FORS2 and the SH. the left panel of Figure 4 where the see­ the contribution of the ground layer with ing measured by the MASS is compared excellent time resolution. to the seeing observed simultaneously by the DIMM. As expected, the MASS The seeing e is linearly proportional to systematically underestimates the ‘real’ wavelength and inversely proportional to Figure 4. Left: Comparison between DIMM and ­seeing because it does not see the tur­ the Fried parameter r . If we assume that MASS seeing (arcsec). The MASS seeing is always 0 smaller indicating a significant contribution from a bulence that is close to the ground. the atmosphere has only two turbulent the ground layer (h < 500 m). Right: Histogram of the Therefore, Figure 4 tells us that a signifi­ layers, a ground layer (GL) and a high-alti­ ground layer seeing contribution.

4 2 000

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The Messenger 132 – June 2008 13 Telescopes and Instrumentation Sarazin M. et al., New Facts about the Evolution of Seeing on Paranal

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0 0 0200 400600 8001000 0.2 0.40.6 0.8 1 Total Ground Layer First Layer (h < 94 m)/Total Ground Layer

2 Figure 5. Left: Cn (h) (h < 94 m) versus total ground resolution between 50 m and 100 m, lence is indeed lower than ~ 15 m above layer turbulence measured by SLODAR. Right: depending on the separation of the dou­ the platform on Paranal. Hereafter we ­Fraction of the total ground layer turbulence that comes from the first SLODAR layer. Most of the ble star and the zenith angle. While will refer to this (low) layer as the ‘surface time the ground layer contribution is dominated by MASS measures the atmosphere be- layer’. the h < 94 m component. tween 0.5 and 16 km, SLODAR mea­- sures below 1 km, so both instruments are nicely complementary (although as Understanding the tude layer (HA), then the total seeing is: stressed above MASS has a much lower inconvenient discrepancy 5/3 5/3 5/3 e T o t = e G L + e H A vertical resolution). Figure 5 shows the distribution of the ratio of the contribu- We can test our hypothesis about the Using this equation we can estimate the tion of the first (SLODAR) layer (h < 94 m) nature of the inconvenient discrepancy ground layer component since DIMM to the total ground layer turbulence deter­ by correcting the DIMM seeing for the measures eTot and MASS measures eHA. mined by combining together DIMM, ground component using the MASS data The result is presented in the right panel MASS, and SLODAR data taken simulta­ and comparing the results with the UT of Figure 4 that shows the histogram neously (Lombardi et al., 2008). The plot image quality as measured by the SH of ground layer seeing. The mean ground shows that most of the time the ground spots. For this comparison we need to layer seeing on Paranal is 0.72? with a layer turbulence is concentrated below know the fraction of the total ground layer rather large dispersion of 0.36?(s) indi­ 94 m. The median value of the distri­ seeing contributed by the surface layer cating that the ground layer varies signi­ bution is 0.86? and the mean 0.82?, but (h < 20 m). The SLODAR data tells us the ficantly with time. So the comparison the distribution is heavily skewed toward average value is ~ 0.8. The best fit shown between MASS and DIMM tells us that a large values indicating that conditions in Figure 6 is obtained for lenslet aberra­ substantial fraction of the seeing on where the ground turbulence is not below tion a = 0.35? and a mean surface layer Paranal originates in turbulent layers be- 94 m are quite rare. The strong turbu­ fraction of 0.8. For these values the least low 500 m altitude. The resolution of lence at a mean altitude of ~ 50 m squares fit (solid line) agrees within 1% MASS does now allow us to say more, revealed by these observations suggests with the X = Y solution, but the histo­ but there are other instruments that can that the inconvenient discrepancy could grams for the two datasets do not over­ get us closer to the ground. be explained if much of this turbulence lap exactly. The best match is obtained is in fact below ~ 20 m, so it is seen for a surface layer fraction of 0.7. This by the DIMM but not by the UT’s. Some is not surprising since, as we have seen SLODAR evidence in support of this hypothesis above, the value changes with time, so comes from the Lunar Scintillometer assuming a constant is just an approxi­ The Slope Detection and Ranging instru­ (LuSci) developed by Tokovinin (2007). mation. The generally good agreement ment (SLODAR) uses an optical trian­ LuSci allows the ground turbulence to be between surface-layer corrected DIMM gulation method on double stars to meas- measured with a resolution of ~ 10 m seeing and UT image quality, however, ure the atmospheric turbulence profile from observations of the lunar disc. A provides convincing evidence that the ­(Butterley et al., 2006). SLODAR, that has very preliminary LuSci test run at Paranal surface layer is indeed the most likely had observing runs on Paranal since in December 2007 indicates that a sub­ explanation for the inconvenient discrep- 2 2005, gives Cn (h) for eight layers with a stantial fraction of the ground layer turbu­ ancy.

14 The Messenger 132 – June 2008 3 3000

a = 0.35� Shack-Hartmann b = 0.8 DIMM, Surface Layer

2 2000 Number

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0 0 00.5 1 1.52 00.5 1 1.5 2 2.5 Seeing Shack-Hartmann UT1 Seeing (arcsec)

Figure 6. Left: Relation between DIMM seeing above that influence the presence and strength the bad seeing occurs when the wind the surface layer determined as described in the of the surface layer. Assuming that the blows warm turbulent air from nearby text, and the UT1 image quality estimated using the size of Shack-Hartmann (SH) spots of the active DIMM/UT discrepancy, ds (see caption of summits along the Atacama fault (which optics. The solid line shows a least squares fit to the Figure 7), measures the strength of the traces most of the road between the data of slope 1.0. The best match of the two lines is surface layer, we can use the Vaisala Panamerican highway and Paranal) over obtained for an intrinsic SH spot size of a = 0.35?, data to check whether the surface layer the top of the mountain. A temperature and a surface layer which contributes about 80% of the total ground layer seeing measured comparing strength correlates with Paranal environ­ inversion of 0.5˚ C is present most of the DIMM and MASS. Right: Histograms of DIMM seeing mental parameters. Figure 7 shows the time on Paranal and there is a weak trend corrected for surface layer and the SH image quality. wind-rose of Paranal ­colour coded ac- of the DIMM/UT discrepancy increasing While the mean values of the two histograms coin­ cording to ds on the left panel, and by with the 2–30 m temperature difference, cide, the overlap is best for 70% surface layer contri­ bution. the difference in temperature between indicating that local conditions may play a 30 m and 2 m on the right panel. The dis­ role in determining the prop­erties of the crepancy is seen to be strongest when When the seeing is bad the wind comes from the NNE and from the SSE (with a broad distribution about Figure 7. Left: The wind-rose of Paranal colour The automated Vaisala weather tower on these directions), while the temperature coded by the discrepancy between DIMM seeing and UT1 image quality; ds = (DIMM5/3 – SH5/3) 3/5. Paranal provides continuous data that gradient is largest when the wind comes Right: Wind-rose coded by temperature gradient we can use to investigate the conditions from the NE and SSE. This suggests that between 2 m and 30 m above ground.

N N ) ) θ θ E E 15 10 5 15 10 5 Wcos( Wcos(

ds < 1� ∆T < 1˚C ds > 1� ∆T > 1˚C ds > 1.5� Wsin(θ) ∆T > 1.5˚C Wsin(θ)

The Messenger 132 – June 2008 15 Telescopes and Instrumentation Sarazin M. et al., New Facts about the Evolution of Seeing on Paranal

1500 1.5

Total Ground Layer High Altitude

1000 1 2 n C

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0 0 0 10 20 30 10 15 20 25 30 35 Month (Since January 2005) Month (Since January 2004)

Figure 8. Left: Evolution of the components of past four years, and from the evolution of bution to have changed over the years. atmospheric turbulence over Paranal (C2) between n the DIMM seeing shown in Figure 1 we The evolution of the wind pattern on 2005 and 2007 determined by combining DIMM, MASS, and SLODAR data (from Lombardi et al., infer that this has been going on for the Paranal since 1985 is shown in Figure 9. 2008). Right: Evolution of the seeing components past 12–15 years. Notice that, just as indi- determined combining the DIMM and MASS data cated by the FORS2 and ISAAC data dis- Figure 9. Evolution of the wind patterns over Paranal as described in the text. played in Figure 1, the high-altitude layer since 1985. The frequency of NE and NNE winds seems to be getting better with time. has increased dramatically since just about the time surface layer (e.g. by confining it to very VLT commissioning started. The S and SSE wind fluctuations have increased such that during some low altitudes). An investigation of this If the surface layer is blown with the wind months the frequency of these winds is also dramati- aspect of the problem is underway, but is over Paranal, we expect the wind distri- cally increased. beyond the scope of this article. 50 25 45 NNE NE Blown with the wind 40 20 35 If our interpretation of the inconvenient 30 15 discrepancy is correct, we expect the 25 surface layer to have become increas- 20 10 Frequency (%) ingly important with time, but the other Frequency (%) 15 components of the seeing to have re- mained constant. Lombardi et al. (2008) 10 5 have examined this question using the 5 combined DIMM+MASS+SLODAR data 0 0 024487296120 14 4168 192216 240264 024487296120 14 4168 192216 240264 taken simultaneously between 2005 and Month (Since January 19 85) Month (Since January 19 85) 2007. Their results, reproduced in the right panel of Figure 8, show that this is 25 14 indeed the situation. The degradation SSE S 12 of DIMM seeing on Paranal is seen to be 20 completely due to changes in the ground 10 layer, while, if anything, the high-altitude 15 layer seems to be getting better. A similar 8 result spanning a longer time interval, 6 10 Frequency (%) albeit with lower altitude resolution, is Frequency (%) obtained comparing the DIMM and MASS 4 5 data only (right panel in Figure 8). The sur- 2 face layer (which as we saw is the main component of the total ground layer) has 0 0 0 24 48 72 96 120144 16 8 192 216 240 264 0 24 48 72 96 120144 16 8 192 216240 264 become significantly stronger over the Month (Since January 19 85) Month (Since January 1985)

16 The Messenger 132 – June 2008 The analysis of the astroclimatology data quality delivered by the VLT Unit Tele­ paigns on existing observatories now (www.eso.org/astclim/paranal) shows scopes, and the notable degradation of underway should be intensified and the that indeed the frequency of ‘bad winds’ DIMM seeing observed over the past results cross-correlated, especially if (NE, NNE, SSE, and S) has increased 15 years have a common origin: the ­different techniques are used. Close over the past 15 years. The seeing is presence of a thin, time variable turbu­ attention must be paid to the local orog­ local, but the wind is global. The change lent layer – the surface layer – over the raphy, and the effects of changes in the in seeing over Paranal is due to changes mountain that is seen by the DIMM, but prevailing winds modelled. Seen through in the wind pattern, which in turn must not by the UT’s. the light of modern site testing tech­ be caused by climate change on a global – The surface layer is strongest when niques and global climate change, it is scale. Fortunately, at Paranal the turbu­ the wind blows from the NNE and from sobering to realise that our ancestor’s lence blown by the wind is very close to the SSE. These winds have become conventional wisdom – put thy telescope the ground, so telescopes high above the increasingly frequent over the past as high above the ground as possible – ground don’t see it. Unfortunately, tele­ 15 years explaining why the surface is still right! scopes close to the ground do! layer appears more and more often. This change in the prevailing winds over Paranal is due to climate change. In fact, References Conclusions it is climate change. Butterley, T., Wilson, R. W. & Sarazin, M. 2006, MNRAS, 369, 835 We can safely draw two quite strong con­ Site testing campaigns must pay close Kornilov, V., et al. 2003, Proc. SPIE, 4839, 837 clusions about the evolution of seeing on attention to the surface layer through Lombardi, G., Navarrete, J. & Sarazin, M. 2008, Paranal: the use of micro-thermal towers, or sensi­ E-ELT-TRE-222-0215, ESO Garching Martin, F., et al. 2000, A&AS, 114, 39 – The discrepancy between the seeing tive astronomical instruments such Tokovinin, A. 2007, Rev. Mex. Astron. Astrophys. measured by the DIMM and the image as ­SLODAR and LuSci. Extensive cam­ (Conf. Series), 31, 61 Photo: S. Brunier

View of the Galactic Centre above La Silla with the domes of the 3.6-m telescope and the CAT illuminated by the setting Moon.

The Messenger 132 – June 2008 17 Telescopes and Instrumentation

EFOSC2 Episode IV: A New Hope

Colin Snodgrass, Ivo Saviane, Figure 1. EFOSC2 Lorenzo Monaco, Peter Sinclaire mounted at the Nasmyth B focus of the NTT. (all ESO)

As part of the long-term plan for the La Silla Observatory, ESO is reducing the number of instruments offered. EMMI and SUSI have been decommis- sioned at the NTT, and EFOSC2 has been moved to the NTT, replacing EMMI, to leave HARPS as the sole instrument at the 3.6-m. Here we describe EFOSC2 and its many capabilities, highlight the changes that the move to the NTT brings, and look forward to future plans for this instrument.

During the Transition Phase (2007–2009), the La Silla Observatory will see a reduc- clusters (Böhringer et al., 2001) and also the globular cluster NGC 3201, in which tion of the number of offered instruments optical studies of supernovae associated the stellar PSF is measured to have a and modes, with the goal of minimising with GRBs (Levan et al., 2005). Now, with FWHM of 0.6?. Figure 3 shows a re-com­ the level of support from the Science Op- the decommissioning of EMMI, EFOSC2 missioning image of the galaxy group erations department. Within this frame­ enters its fourth tour of duty, and returns Arp 321. At the NTT we measured the work, starting from Period 81, EFOSC2 is to its original home at the NTT (Figure 1). pixel scale to be 0.12?/pixel, the rotation offered at the NTT instead of the 3.6-m centre to be near the centre of the CCD telescope, initially together with SOFI. In One of the main reasons for the longev- at pixel (1016, 990), and the orientation April 2008 the instrument was transferred ity and reliability of EFOSC2 is the fact at zero rotator angle to be North up and to its new home, the Nasmyth B focus that its design is relatively simple, and yet East right. This information has been of the NTT. Here we recall some of the it offers many observing modes and is used to allow full World Coordinate Sys­ long history of EFOSC2 and its many ca- highly versatile. It has undergone various tem (WCS) information to be stored in pabilities, and describe the changes that improvements over the years, the most the FITS headers of data taken with the move to its new telescope brings. recent being the addition of a quarter EFOSC2, which was shown in tests to be wave plate for polarimetry (Saviane et al., accurate to within the typical pointing EFOSC2, the second ESO Faint Object 2007) and new high-resolution volume- accuracy of the NTT (a few arcseconds). Spectrograph and Camera, was originally phase holographic grisms (see following built by ESO staff at La Silla for the NTT, article by Saviane & Monaco). to provide an imager and spectrograph for the first commissioning work and early scientific programmes before EMMI was Return to the NTT ready. The design concept was based on the robust and versatile original EFOSC With the move back to the NTT, some on the 3.6-m, but with various im- further changes were implemented, most- provements including a larger CCD (see ly due to the change of focal station from ­Buzzoni et al., 1984 and Eckert et al., the f/8 Cassegrain focus of the 3.6-m to 1989). It saw first light on the NTT on the f/11 Nasmyth focus of the NTT. The 11 May 1989, and the catalogue of Plane­ observing modes offered at the NTT are: tary Nebulae that came from commission- Broad- and Narrowband Imaging; Coro­ ing observations for this telescope re- nographic Imaging; Polarimetric Imaging; mains EFOSC2’s most popular paper Long-Slit Spectroscopy; Multi-Object (Schwarz et al., 1992). Once EMMI arrived Spectroscopy; Slitless Spectroscopy; at the NTT in 1990, EFOSC2 was moved and Spectropolarimetry. All of these to the 2.2-m telescope, before moving modes were successfully tested during in October 1997 to the 3.6-m, where it recommissioning on the NTT in April replaced the original EFOSC and served 2008. Figure 2. An image of NGC 3201 taken to demon­ for over 10 years. Scientific highlights strate the image quality. The stellar Full Width at Half Maximum (FWHM) of the star images in the R-band from the instrument during this time The image quality of EFOSC2+NTT is was measured to be 0.6?, matching the DIMM see­ include work on dark matter in galaxy very good: Figure 2 shows an image of ing.

18 The Messenger 132 – June 2008 The field of view of the full 2 048 × 2 048 higher demand than all VLT instruments pixel CCD is 4.1; × 4.1;, although there is except FORS2 and VIMOS, even with some vignetting at the corners of the the end of service mode observing at CCD, beyond a radius of approximately La Silla. With the end of EMMI operations, 2.4; from the centre, which corresponds EFOSC2 now takes on the considerable to approximately 8 % of the full field of load of being ESO’s only general-purpose view. There is also some distortion of the imager and spectrograph on a mid-size image PSF in the radial direction due telescope. With this in mind we are also to the focal reducing optics of the instru­ planning further future improvements to ment, which was measured to reach 10 % the instrument: We are in the process beyond approximately 2; from the centre. of looking for a good replacement CCD The lower pixel scale means that stellar that would give improved readout noise PSFs are oversampled in all but the best and readout speed, and would be com­ seeing, so higher ­binning modes than patible with a continuous flow cryostat the current standard 2 × 2 will be offered to simplify operations and providing im- for imaging (3 × 3 and 4 × 4; also 1 × 3, proved long-term stability. Implementa­ 1 × 3, 2 × 3 and 2 × 4 modes for spec­ tion of calibration OB’s (CALOB) and a full troscopy). These modes still remain to reduction pipeline will also enhance oper­ be implemented, but are expected to be ations in the near future. We look forward offered during the first half of P81. The Figure 3. The interacting galaxy group Arp 321, to many more years of exciting science high sensitivity in the blue is maintained taken as a test image during the recommissioning. with EFOSC2 in its new home. following a UV-flooding of the CCD during the move, while the response is better at the telescope pointing. Measurements red wavelengths than it was at the 3.6-m. of both polarised and unpolarised stars at Acknowledgements The zero-points for UBVRI are shown many telescope positions were taken We thank all the members of the La Silla staff in Figure 4. The fluxes for a 15th magni­ during the commissioning time, and the involved in the transfer of the instrument to the NTT, tude star in e-/sec are U = 5.7 × 103, B = instrument polarisation as a function who ensured not only a smooth move, but also 2.9 × 104, V = 3.3 × 104, R = 3.5 × 104, I = of telescope position is now being mod­ took the opportunity to carry out numerous improve­ 1.5 × 104. elled. ments that have been on the Instrument Scientist ‘wish list’ for some time. In the spectroscopic modes the change of plate scale means that the old slits The future of EFOSC2 References have different effective widths, so new Böhringer, H., et al. 2001, A&A, 369, 826 slits with 0.3?, 0.5?, 0.7?, 1.0 ?, 1.2 ?, 1.5 ?, The demand for all of EFOSC2’s observ­ Buzzoni, B., et al. 1984, The Messenger, 38, 9 2?, 5? and 10? widths have been pre­ ing modes remains high. With 51 propos­ Eckert, W., Hofstadt, D. & Melnick, J. 1989, pared, each with a length of 4.1; (i.e. cov­ als submitted for P82, it is the most highly The Messenger, 57, 66 ering the full field of view). The default requested La Silla instrument, while in Levan, A., et al. 2005, ApJ, 624, 880 Saviane, I., et al. 2007, The Messenger, 129, 14 slit alignment is in the East-West direction terms of time requested (8 % of total time Schwarz, H. E., Corradi, R. L. M. & Melnick, J. 1992, (horizontally across the chip), so to align requested on all ESO instruments) it is in A&AS, 96, 23 the slit along a given Position Angle, an offset of PA + 90˚ must be applied to the rotator (this is done automatically when presetting to the parallactic angle). During commissioning it was found that, with R the instrument now mounted horizontally V at the NTT Nasmyth B focus (instead of B vertically at the 3.6-m Cassegrain), there 26 is significant flexure. A shift of 3.5 pixels in the spectral (y-axis) direction was meas- I ured over the full rotator motion. Further work is planned to stiffen the instrument, but those users wanting to measure 25 radial velocities are advised to take regu­ Zero-point (mag.) lar arc lamp exposures. U Figure 4. The UBVRI zero points of The polarimetry modes of EFOSC2 are EFOSC2 (with CCD No. 40) on the 24 the most strongly affected by the move, NTT. The new values (green open cir­ cles) compare favourably with the as the reflection from the NTT M3 intro­ 400500 600700 800 mean values (blue open triangles) for duces linear polarisation dependent on Wavelength (nm) the same instrument on the 3.6-m.

The Messenger 132 – June 2008 19 Telescopes and Instrumentation

Two Volume-phased Holographic Grisms Now Available for EFOSC2

Ivo Saviane, Lorenzo Monaco (ESO) to have very short exposure times for this dance at the star surface. Assuming lamp, of the order of 0.1 sec. Redder than that a star is born with a meteoric Li ~ 7000 Å fringes are visible in the flat-field abundance (ALi ~ 3 dex), standard mod­ Starting from Period 81, two new vol- frames of the red grism. els predict that in giants the Li abun­ ume-phased holographic grisms are dance should not exceed ~ 1.5 dex. Yet, available to be used with EFOSC2. Test- Arc lamp exposures were used to meas­ about 1–2 % of K giants have Li abun­ ing of the grisms is described. Some ure the dispersions and resolutions, which dances exceeding this value. A few of results on measurement of the stellar are listed in Table 1. Note that at the them even have a Li abundance similar or Lithium doublet and galaxy rotation extremes of the spectral range the reso­ larger than the meteoric value. curves demonstrate the performance of lutions are degraded by ~ 50 % for the the new grisms. blue grism and ~ 30 % for the red grism. The occurrence of Li-rich stars is usually The highest dispersion of the current explained in terms of a Li-production EFOSC2 grisms is 1 Å/px, so the blue and mechanism (Cameron & Fowler, 1971) in Two volume-phased holographic grisms red VPH grisms offer values three and the stellar interior associated with a cir­ (VPHG) were procured by the ULTRA- two times larger than what is currently culation mechanism to bring the pro­ SPEC project (see Dihllon et al., 2007), available, respectively. Plots of the wave­ duced Li to the star surface. However, a and were first used in January–February length calibrated arcs are shown in Fig- complete theory capable of explaining 2008 for some of the science runs. ure 1. all the observational facts is still miss- ­Afterwards, the VPHGs were tested for ing and particularly puzzling is the case of scientific performance, and on the basis The two technical nights at the 3.6-m low-mass stars (e.g., Charbonnel & of the overall positive evaluation, it was tele­scope were not photometric, so sys­ Balachandran, 2000; Uttenthaler et al., decided to offer them to the community. tem efficiencies were obtained later with 2007). Here we report on some of the tests that EFOSC2 at the NTT. They are shown in were performed on 13 and 14 February Figure 2, together with the efficiencies For this reason, in parallel with improving 2008. At that time the instrument was of the other grisms. The efficiency of the models, data are being collected to installed at the 3.6-m telescope; during blue VPHG goes from 30 % at the red ­construct a more complete observational the commissioning of EFOSC2 at the end, down to 20 % at the blue end. The picture. The Li abundance is routinely NTT (April 2008) the tests were repeated red VPHG has a more constant response, measured using the doublet at 6707.8 Å. to assess the performance at the new with an efficiency around 30 %. In gener- To test the feasibility of such a measure­ focal station. The basic parameters of the al, as Figure 2 shows, the system efficien­ ment, we took spectra of three stars two grisms are summarised in Table 1. cies are comparable to those obtained with different equivalent width (EW) of the with the existing EFOSC2 grisms. Li doublet. The extracted and continuum- normalised spectra are shown in Fig- Basic characteristics In order to determine whether the grisms ure 3, with signal-to-noise ratios better are useful to obtain valuable science than 50. Clearly EWs of the Li line down To characterise the grisms the usual set data, we took spectra to measure stellar to 300 mÅ can be easily measured, of calibration frames were taken: bias abundances and to study the kinematics while the star with a 200 mÅ line is more frames, one arc frame, and dome flat-field of spiral galaxies. ambiguous, because of its late spec- frames. In both cases, it was soon evi­ tral type. The doublet is probably de- dent that part of the CCD is not illumi­ tected, but a confirmation with an earlier nated because, after passing through the Measurement of Lithium line 6707.8 Å type star is needed. VPHG, the beam suffers a deviation in the spatial direction. Only ~ 70 % of the Lithium is a fragile element which is easi- field of view is available when using ly destroyed in stellar interiors at rela- Rotation curves of spiral galaxies the red VPHG, and ~ 65 % when using tively low temperatures. As a star ap- the blue grism. In terms of pixels, the proaches the giant phase, the deepening Rotation curves of spiral galaxies are useful area is 2 021 × 1411 px for the blue of the convective envelope brings to the used to study their kinematics, in the grism, and 2 021 × 1231 px for the red star surface material which was depleted search for the amount and distribution of grism. Some reflections are also visible in in Li in the stellar interior. Such mixing dark matter (DM), which are constrained the arc frame of the red grism, caused of Li-depleted and unprocessed material by departures from the expected veloc- by the Helium lamp. It is thus suggested causes an overall dilution of the Li abun­ ity curve of a rotating disc. The rotation

Grism Lines/mm lmin lcen lmax RS nm/px FWHM Binning Slit Table 1. Parameters of VPHGs provided by #19/475 1557 444 478 511 3 2001 0.034 0.15 1 0.5? the ULTRASPEC team. Wavelengths are measured in nm. 3 200 0.067 0.15 2 0.5? 2 200 0.067 0.21 2 1.0 ? 1 A resolution greater than 4 000 is found by Vik #20/656 1070 605 660 714 3400 0.055 0.20 1 0.5? Dhillon with Ultraspec; investigations are on- 3000 0.108 0.22 2 0.5? going to see whether EFOSC2 can match this per­ formance. 2000 0.109 0.33 2 1.0 ?

20 The Messenger 132 – June 2008 Figure 1. Wavelength- 5 000 10 000 calibrated spectra of the Helium + Argon arc lamps taken with the 4 000 8 000 blue VPH grism (left) and the red VPH grism (right). The high back­ ground in the red arc 3 000 6 000 can be reduced by decreasing the exposure time of the He lamp. Pixel value 2 000 Pixel value 4 000

1000 2 000

0 0 4400 4600 4800 5000 6 000 6200 6400 6600 6800 7000 Position (Pixel) Position (Pixel)

0.4

HD90082: 200 mÅ 0.3 19 20 2 8 0.2 e–/photon 0.1 HD95799: 335 mÅ 11 1.5 2 0 400600 8001000 λ (nm) IRAS13539-4153: 630 mÅ

Figure 2. System efficiency given by the blue VPHG Normalised continuum 1 #19 (blue curve) and the red VPHG #20 (red curve) compared to that of other EFOSC2 grisms.

curves also offer clues on the role of 0.5 interactions and their impact on evolu­ 6600 6650 6700 tionary histories. Galaxy evolution in Å ­general can also be explored by com­ paring rotation curves of distant galax- momentum properties and the DM distri­ Figure 3. A portion of the spectrum of three stars ies with those of nearby objects. bution on the 100 kpc scale. with different EWs of the lithium doublet at 6707.8 Å (see the labels above each spectrum). The spectra have been obtained with the red VPHG, and the Rotation curves derived from emission To measure rotation curves of giant spiral dashed vertical segments mark the position of Ha lines, and in particular those of Ha galaxies we took spectra of two objects (left) and the Lithium doublet (right). and [N ii] are particularly useful to derive with the red VPHG. A 1200-sec exposure the mass distribution in disc galaxies, was made of the giant spiral UGC 5711, The same exercise was done with PGC because they trace the motion of inter­ with the slit oriented along its major axis 048532, whose rotation curve is also stellar gas of the young population (H ii (see Figure 4). A portion of the 2D spec­ ­displayed in Figure 5. As for UGC 5711, regions). This gas has a velocity disper­ trum near Ha is also shown in Figure 4. the quality of the data is very good out sion (of the order of 5–10 km/s) that is The differential velocity can easily be to 10 kpc. For this galaxy, Yegorova et al. much smaller than its rotational velocity, seen on the frame, and the rotation curve (2008, in preparation) obtained an in­- allowing accurate measurements. Among is plotted in Figure 5 out to ~ 30 kpc. The dependent rotation curve with a 2 × spiral galaxies, giant spirals seem to be figure shows that the systemic velocity 2 000 sec spectrum collected with grat­ the best laboratories to study the struc­ is compatible with that of the RC3 cata­ ing 6 of the EMMI/REMD arm. The reso­ ture and kinematics (see Figure 5). They logue, and that the precision we obtain is lution was 4 900 with a slit width of 1?. have extended discs and rotational veloc­ comparable to that of standard studies of The resulting rotation curve is shown with ities up to ~ 400 km/s. Through their ro- this kind. open circles in Figure 5. It is clear that the tation curves we can study the angular two curves are consistent with each

The Messenger 132 – June 2008 21 Telescopes and Instrumentation Saviane I., Monaco L., Two Holographic Grisms Now Available for EFOSC2

Figure 4. The left panel contains the acquisition ards to be obtained in the same position Acknowledgements image of UGC 5711 in white light, showing the loca­ as the targets. For extended sources tion of the slit across the galaxy. The right panel We thank Irina Yegorova and Alessandro Pizzella for shows the wavelength-calibrated and distortion-free the spectrophotometric standards should computing the kinematic data of the spiral galaxies. spectrum in the region of Ha. The wavelength be placed in different positions across increases upward. the CCD, or corrections to some fiducial response function should be obtained References other, demonstrating the suitability of the based on flat-fields. Second order con­ Cameron, A. G. W. & Fowler, W. A. 1971, ApJ, 164, red VPHG for this kind of study. More­ tamination is apparent in the red grism 111 over, the EFOSC2 result was obtained in for l > 6 800 Å, so it is advisable to use Charbonnel, C. & Balachandran, S. C. 2000, A&A, a 70 % shorter exposure time. order-sorting filters to cut out the blue 359, 563 Dhillon, V., et al. 2007, The Messenger, 127, 41 flux, if flux calibration is an issue for the Uttenthaler, S., Lebzelter, T., Palmerini, S., et al. science case. Note also that the spectral 2007, A&A, 471, L41 Caveats range of the blue grism does not reach the Mg triplet at 5 200 Å or the G-band To make the best use of these grisms, at 4 300 Å. However, using the movable users must be aware of the following slit we verified that the two features issues. The flat-fields of both grisms show can be reached with a slit offset of 15 mm Figure 5. Left: The rotation curve of UGC 5711 gradients in the cross-dispersion direc­ in either direction (the dispersion is measured with the red VPHG. The dotted line shows the recession velocity of 6264 km/s from RC3. tion. These gradients are also wave­ 14.5 Å/mm). Therefore two additional sets Right: The rotation curve of PGC 048532 measured length-dependent, which means that the of slits were made, with 15 mm offsets with the red VPHG (filled diamonds + error bars) response functions depend on the posi­ to the blue and to the red, with respect to compared to the result (open circles) obtained with tion along the slit. For point sources, an a central slit. They can be used to cover EMMI by Yegorova et al. (2008, in preparation). The dotted line shows the recession velocity of accurate flux calibration then requires the a more interesting blue spectral range, by 8587 km/s from RC3. The physical radii have been –1 –1 spectrum of spectrophotometric stand­ merging two spectra. computed assuming H0 = 72 km sec Mpc .

∆r (kpc) ∆r (kpc) –10 0 10 –10 –5 0 5 10 8800 UGC 5711 6400 8700

8600 km/s 6200 km/s 8500

8400 PGC 048532 6 000 –500 10 –20–10 01020 ∆RA (�) ∆RA (�)

22 The Messenger 132 – June 2008 Telescopes and Instrumentation

The ALMA Antenna Transporter

Max Kraus, Stefano Stanghellini, to the observation site within one work loading to the antenna-foundation cou­ Pascal Martinez, Franz Koch, shift of six hours. These requirements pling can be achieved quickly and safely. Martin Dimmler, Jean Michel defined the transport capacity and led to The coupling interfaces were defined ­Moresmau, Hans Rykaczewski the need for two transporters. such that the various antenna types can (all ESO) use one standard interface. During the site selection phase, the geo­ graphical conditions related to transport Close cooperation was necessary with The ALMA observatory will consist of were studied, since the roads are also a the scientists defining the antenna array an array of 54 12-m diameter and 12 7-m primary component of antenna transport. configuration of the central cluster, where diameter antennas. In order to configure The cost of the roads easily exceeds the antennas are placed as close to- the different array modes, it is neces- the cost of the transport vehicle. It was gether as possible. For efficient reconfig­ sary to move the antennas to different decided early in the planning phase to uration, and in case an antenna needs configurations. In the compact array build a dedicated road from the selected repair, it is necessary to carry antennas configuration, the antennas are packed basecamp location (the Operations Sup­ out of any location. After several iterations, as closely as possible within a circle of port Facility, OSF) at 3 000 m altitude up transport passageways were designed 200 m diameter; in the extended con­ to the observation site (the Array Opera­ into the antenna patterns to allow any figuration the antennas are spread over tions Site, AOS). The decision to build this antenna to be reached efficiently. The tol­ an area of about 15 km in diameter. The road then allowed the definition of the erance on the passageways limited frequent relocations of antennas will road parameters to be fed into the speci­ the maximum dimensions of the trans­ be accomplished by two special vehi- fication for the transporter. Together with porter. The early definition of the inter­ cles, the ALMA Antenna Transporters. the site engineers the main road parame­ faces and main parameters was a neces­ The challenges encountered during ters were defined, with feedback from sary process in order to allow the Call their development and their main char- the basic parameters of the transporters for ­Tender for industrial contracts for the acteristics are described. (such as dimensions and weight). The transporters to be drafted. second important and obvious compo­ nent of the antenna transporters is their Definition of requirements and interfaces attachment to the antennas. After a first Early concepts survey of possible industrial solutions for Already in the early design phase of heavy transport vehicles and, in discus­ In parallel with the discussion and defini­ ALMA, the basic requirements for the sion with the teams developing the proto­ tion of requirements, the available in- ALMA Antenna Transporters were type antennas, the necessary details of dustrial solutions for heavy transport in defined. They should, for example, have attachment flanges on the antennas were the class of 50 to 100 tons were studied. rubber tyres and be capable of nego­ defined. Already proven industrial concepts were tiating slopes up to 15 %. Later more preferred in order to reduce development detailed requirements were added, such A third important design consideration for risk and cost and achieve a more reliable as the capability to move four antennas an antenna transporter is the interface transport concept. First ideas were a day for array reconfiguration, or trans­ between the antenna and the foundation. based on mining dump trucks or a mobile port one antenna from the basecamp After a transporter lifts off an antenna and crane (see Figures 1 and 2). sets it down on a foundation, the anten- Figure 1. Antenna transport CAD layout based on a na is required to perform without realign­ mining dump truck. Upper: Front and side views ment. The lifting and lowering mechanism of an antenna transporter. Lower: Close passage in Figure 2. Transporter concept using a large mobile central cluster is shown in side (left) and top (right) of the transporter has to be designed crane (to be used in combination with rented trans­ views. such that reliable and precise loading/un- port vehicles).

The Messenger 132 – June 2008 23 Telescopes and Instrumentation Kraus M. et al., The ALMA Antenna Transporter Photo: Scheuerle Fahrzeug GmbH

Figure 3. Advanced transporter one of the studies showed that a hydro­ Figure 4. Transporter ­concept based on an industrial dump static drive for all wheels, instead of just design with hydro­ truck, which is shown on the right. statically driven wheels. the prime mover, has advantages: the total vehicle weight is reduced and the Further studies showed that a transport traction on critical road conditions is tracts were signed, a common antenna concept requiring a minimum road ­improved. A vehicle with a U-shaped transport interface was designed at ESO width and low wheel loads is the most frame and a large number of hydrostati­ and agreed with all teams involved in the economic, since the majority of the cally driven wheels was selected as a antenna design. With the specifications investment costs for antenna transport baseline concept (Figure 4) for the ten­ all agreed, the tendering process could would go into road construction, not dering process carried out by ESO. be started and resulted in a contract with into vehicle production. This resulted in a the German company Scheuerle Fahr- concept derived from a so-called ‘slag zeugfabrik GmbH (www.scheuerle.com). pot carrier’ used in the metallurgy indus­ Specification, tendering and contract Scheuerle is a world market leader in try and consisting of a prime mover hydrostatically propelled module and and a load trailer (see Figure 3). This con­ From the internal studies and the two shipyard transporters and regularly builds cept was further developed and later industrial studies, sufficient material was transporters with capacities of 1000 tons investigated by two industrial feasibility collected to write a detailed technical or more. Loads up to 16 000 tons have studies. These studies confirmed the specification for the ESO tendering proc­ been successfully moved with their equip- ­feasibility of this early ESO concept, but ess. Before the production antenna con­ ment. Scheuerle has all the required de- Photo: A. Schilling, Scheuerle Fahrzeug GmbH

Figure 5. Transport with dummy load during loading sequence test.

24 The Messenger 132 – June 2008 tal capacities. Handling and transporting heavy loads is always dangerous and special care and experience is required. To allow safe operations under the high altitude conditions, various safety inter­ locks and supervision systems have been developed and built into the control sys­ tem of the transporters to prevent dan­ gerous operations when commanded by the operator. Photo: A. Schilling, Scheuerle Fahrzeug GmbH

Transporter design features

For the final design, an open U-frame lay­ out was selected. On top of the vehicle is the loading system with two ramps which slide the antenna, after pick-up, to the centre of the vehicle. This design allows a relatively low weight of the vehicle and distributes the antenna weight evenly on Figure 6. Both trans­ the axles during driving. The loading sys­ porters parked at tem has two x-y-tables on each side the OSF at the end of acceptance. which take the antenna on two dedicated brackets mounted permanently on the antenna transport flanges. These -x y- sign capacity in-house and collaborates Another challenge addressed during the tables can position the antenna precisely closely with an established network of design and production phase was the on top of the station before setting down. suppliers of major components, such as operation of the vehicle at the very high Strong pins and automatic clamps block Deutz AG for the engines, Mannesmann altitude of 5000 m. Little experience the x-y-tables during transport to secure Rexroth AG for the hydraulic drive sys- exists in the relevant industries with ma- the antenna. tem or Kessler & Co GmbH for the axles chines operated under these conditions with brakes. At the Scheuerle premises and most major components are rated On top of the frame are two identical in Pfedelbach near Heilbronn (Germany), for altitudes not exceeding 3 000 m. Spe­ engine units to power the transporter and the required manufacturing, assem- cial sub-contracting conditions were a generator unit to supply the antenna bly and testing facilities were all available. ­necessary to ensure operation under the with electric power during transport. This required environmental conditions. The latter is necessary to maintain the cryo­ high altitude with the reduced oxygen genic cooling of the antenna which Design challenges content also affects humans with the con- remains operational during transportation sequence of reduced physical and men­ and avoids warming up of the cooled In the early design phase a promising vehicle concept was quickly developed based on the results of the bidding ­process. But it soon became clear that the selected concept could not easily be realised, because the layout relied on large wheels with tyres from the earth- moving industry. These very large tyres were sold out at that time and no sup- plier could be found who could provide the tyres reliably within the required de- Photo: A. Schilling, Scheuerle Fahrzeug GmbH livery time of about 15 months. As a con­ sequence, a new vehicle layout had to be developed, calculated and investi­ gated based on a larger number of smaller wheels which were available in the required production schedule. Figure 7. Fast downhill test drive on the road between the OSF and AOS.

The Messenger 132 – June 2008 25 Telescopes and Instrumentation Kraus M. et al., The ALMA Antenna Transporter

detector systems. Both engine units are Fuel capacity: 2 × 1500 l, diesel Support system: redundant and allow operation at re- Wheels: 28 × 6.00 R20 (1.35-m diameter) – Hydraulic support with 600 mm vertical duced speed with one engine only (see on 14 axles stroke on each axle Figure 9). All critical components are con­ Three brake systems: – Interconnected to 3 groups for ­isostatic centrated in the engine unit, which can – Emergency and park brake: spring support be replaced within a few hours in case of operated (hydraulically opened) on all – 2 additional outriggers for loading fault or for maintenance. wheels Loading system: – Service brake: oil immersed multiple – Loading time: < 20 min Below the frame is the driver cabin for disc brakes on all wheels with oil circu­ – Unloading time: < 20 min two persons. This position was selected lation – Antenna adjustment on foundation: for safety reasons because all the wheels, – Continuous brake: engine brake with > 150 mm in all directions and the edge of the road, are in the direct exhaust flap on all engines field of view of the driver. It is equipped Drive system: with all controls and monitors for the cam- – 2 pumps with variable flow rate on each Damping system eras mounted on all corners and other engine critical areas of the vehicle. During the – 1 hydrostatic oil motor in each axle During the specification of the interface loading process and in other critical situ­ – Differential lock and overdrive protec­ between antenna and transporter, the ations, the vehicle can also be operated tion in each axle maximum possible oscillation of the an- from a remote control panel with fail- – Max speed unloaded: 20 km/h (soft­ tenna during transport was carefully stud­ safe radiolink. Except for the safety func­ ware limited) ied. The antenna is a piece of precision tions of the service brake and the emer­ – Max speed loaded: 12 km/h mechanics requiring delicate alignment of gency stop system, all functions of the – Speed limit with overspeed protection the reflector surface. Investigations con­ transporter are controlled via computers depending on road slope cluded that preparatory studies could not and specially developed software. – Max slope: 15 % be performed because the outcome Steering system: depended primarily on the performance The wheels are mounted in pairs on – Steering angle +/– 70 deg hydraulically of the tyres, and no reliable tyre data boogies with swing axle and hydraulic actuated on each axle could be obtained from the manufactur­ support. All boogies are identical to – Electronically controlled by a safety ers. Therefore the problem could only ­facilitate maintenance. In case of a failure ­certified system be solved at that stage by adopting con­ of one boogie the faulty boogie can be – 4 selectable steering programmes servative estimates and specifying large lifted and operation can be continued with reduced speed. The transporters are also equipped with a vehicle positioning system and an anti-collision system. The positioning system consists of a rotat- ing laser installed on the antenna founda­ tions and laser sensors on the vehicle. The sensors guide the driver to the final unloading position with a precision of a few centimetres. The anti-collision system consists of four laser scanners and a Photo: A. Schilling, Scheuerle Fahrzeug GmbH numbers of ultrasonic sensors. The laser scanners detect the structures of nearby antennas before the driver comes too close to them and would stop the trans­ porter, after a warning, to avoid collisions. Both systems will ensure safe operation also under the difficult high altitude con­ ditions.

Technical data

Weight (empty): 132.5 tons Max. payload: 115 tons Engine power main engines: 2 × 500 kW (2 × 320 kW @ 5 000 m) Figure 8. Uphill test Electric power generator: 100 kW drive with dummy load on road between (ca 50 kW @ 5 000 m) OSF and AOS.

26 The Messenger 132 – June 2008 Figure 9. One of two installed engine units. Each unit is self-sufficient and can be quickly changed in case of problems. One unit is capable of mov­ ing the transporter in cases of emer­ Hydraulic oil tank gency. (Figure: Scheuerle Fahrzeug Fuel tank GmbH)

Flushing brake oil tank

Air cleaner Pump drive Oil cooler Electrical engine cabinet Space for an automatic extinguisher Hydraulic pumps

Water and charge air Exhaust cooler Diesel engine

margins in the interface control docu­ final system was designed and imple­ The first ALMA Antenna Transporter was ment. The experience at ESO in calculat­ mented just before the vehicle left the completed in July 2007 (see ESO PR ing and specifying earthquake loads from factory. 32/07) and given the name “Otto” at a the VLT were very helpful in this study. naming ceremony at the Scheuerle f­actory (see ESO PR 45/07). The second Provisions for adding a damping system Into operation transporter was completed shortly after in the transporter specification were and was named “Lore”. Both transporters defined, but the damping system was ex- Although only an auxiliary logistic system were then shipped to Chile and arrived cluded from the contract since the spe­ for the ALMA observatory, with techno­ at the OSF on 14 Februrary 2008. They cialist know-how for simulation was not logies coming from completely different were successfully commissioned at available in the relevant industries. Later areas compared to the other components the OSF in the following months and will in the project, when the design was fin­ of ALMA, the transporters are funda- enter service moving the first antennas, ished and the entire vehicle performance mental for the achievement of the scien­ which are currently being commissioned data were available, further studies could tific objectives of the observatory. High at the OSF, to the Chajnantor plateau. be conducted by ESO on this subject. reliability and availability of the transport­ It became evident that under certain road ers are essential for minimal observa- conditions with a washboard profile, tory down time. With the early collabora­ References ­dangerous excitations of the vehicle and tion between ESO, the international Haupt, C. & Rykacewski, H. 2007, The Messenger, the antenna could occur. Consequently ALMA partners and industry, good tech­ 128, 25 a damping system was necessary. Using nical solutions could already be devel­ the ESO capabilities for dynamic simu­ oped and realised in the project definition lations, usually employed for simulating phase. The anticipation of potential prob­ the performance of telescope systems, lems and the configuration control of the damping behaviour of the transporter interfaces and specifications has allowed was simulated and the components for parallel and undisturbed development of a damping system were identified. With antennas, transporters and the site infra­ the help of the Scheuerle engineers, the structure.

The Messenger 132 – June 2008 27 Telescopes and Instrumentation

Recent Progress at the ALMA Test Facility

Robert Laing (ESO) astronomers from Garching and Santiago participate in science operations, again in collaboration with colleagues from else­ Recent developments at the ALMA Test where in the project. Finally, astronomers, Facility are presented. Many aspects of array operators, hardware and software the hardware and software needed for engineers from the Joint ALMA Office are operation in Chile have now been tested spending substantial periods of time at and the Facility continues to demon- Photo: R. Aviles, Joint ALMA Office the ATF, training to support ALMA in Chile strate its value as a test-bed. The first but also contributing greatly to develop­ high-resolution interferometric spectra ment, testing and debugging. The work at of astronomical sources have now been the ATF is recognised as vital to ALMA’s obtained. success, and is likely to continue to 1 September 2008, when some of the Figure 1. The two ALMA prototype antennas during equipment will be required for interfer- The ALMA Test Facilty (ATF) is located an interferometric observation. The European and ometry in Chile. North American antennas are on the left and right, at the site of the National Radio Astron­ respectively. omy Observatory (NRAO) Very Large Array near Socorro, New Mexico, USA. It References was used initially to test the three proto­ lator can be configured in many different Hunter, T. & Laing, R. A. 2008, The Messenger, 131, type antennas developed by Vertex RSI ways. The published spectrum was an 47 (North America), the AEC consortium example of ALMA’s lowest resolution (Europe) and MELCO (Japan). A photo­ mode, in which spectral channels cover graph of the three antennas at the ATF a total frequency range of 2 GHz. This appeared on the cover of The Messenger would be used with the final array to 25 3 ? ? N N 3 128. The MELCO prototype has since obtain the widest possible bandwidth and 3 SH SH SO CO 3 3 2 HC HC OCH 3 OCHO OCHO OCHO CH CH CH 3 3 been dismantled and some of its struc­ hence the highest sensitivity. 20 3 CH CH CH ture re-used for one of the production an- CH tennas currently under test in Chile. The In January, many of the operations 15 remaining two antennas (Figure 1) have needed to set up the interferometer had 10 been used to develop and test much to be performed using separate pieces of the hardware and software required for of software. Over the last few months, 5

ALMA to operate in Chile. there has been steady progress towards 0 10 5 1.001 10 5 1.002 10 5 1.003 10 5 1.004 10 5 1.005 10 5 the goal of automated operation. A sci­ Rest Frequency (MHz) Until September 2007, the emphasis at ence project can now be created using 25 2 the ATF was primarily on Prototype Sys­ the ALMA Observing tool, archived and N 3 CN OH 2 3 SO HC OCHO CH CH 3 tem Integration – the process of inte­ then executed using the scheduler. The 20 3 CH grating and testing the ALMA electronics. results are stored in the format of the CH Since then, the Facility has been man­ ALMA Science Data Model, exported 15 aged by the Computing Group. The em- to the CASA data reduction package and 10 phasis is much more on software devel­ reduced. As an example, we show a opment, with considerable input from higher-resolution spectrum of the Orion 5 astronomers, although testing of produc­ Hot Core (Figure 2). In this observation, 0 1.005 10 5 1.006 10 5 1.007 10 5 1.008 10 5 1.009 10 5 1.01 10 5 tion electronics in advance of deploy- the Tunable Filter Bank cards developed Rest Frequency (MHz) ment to Chile continues to be important. at the University of Bordeaux were used The major milestone of dynamic interfer- to increase the resolution of the correla­ 25 CS OH CO 2 3 2 H H ometry was achieved in November 2007. tor. Figure 2 shows three portions of a 20 CH This meant that the antennas could be spectrum with 2048 channels across the pointed at an astronomical source, with 2 GHz band from 100–102 GHz. Many 15 the receivers tuned and the correlator astrophysically important molecular lines 10 under computer control, so that stable can already be identified on this spec­ interferometric fringes were obtained. We trum. 5 showed an example of an interferometric 0 1.01 10 5 1.011 10 5 1.012 10 5 1.013 10 5 1.014 10 5 1.015 10 5 spectrum of the Orion Hot Core region The ATF is managed by NRAO and a Rest Frequency (MHz) obtained in January 2008 in a recent substantial part of its support involves Messenger article (Hunter & Laing, 2008). staff based in Socorro, but it is very much Figure 2. A spectrum of the Orion Hot Core region ALMA does not differentiate between an international operation. Software engi­ obtained with the prototype interferometer at the ATF continuum and spectroscopic configura­ neers from ESO and its partner institutes by Al Wootten. There are 2048 spectral channels over a total bandwidth of 2 GHz. Prominent lines of tions: all ALMA observations will have in Europe are frequent visitors, as are astrophysical interest are labelled. (Credit: A. Woot­ multiple spectral channels, and the corre­ their counterparts from East Asia. ESO ten, NRAO)

28 The Messenger 132 – June 2008 Telescopes and Instrumentation

Cute-SCIDAR at Paranal for E-ELT Site Characterisation

Héctor Vázquez Ramió1 Marcos Reyes1 José Miguel Delgado1 Elvio Hernández1 Miguel Núñez Cagigal1 Jesús J. Fuensalida1 Gianluca Lombardi 2, 3,4 Frédéric Derie 2 Julio Navarrete 2 Marc Sarazin 2

1 Instituto de Astrofísica de Canarias, Spain 2 ESO 3 National Institute for Astrophysics, ­Bologna Astronomical Observatory, Italy 4 University of Bologna, Department of Astronomy, Italy

A new version of the cute-SCIDAR instrument, which employs the general- ised SCIntillation Detection And Rang- Azouit, 1983; Vernin & Muñoz-Tuñón, Figure 1. Top left: Normalised autocorrelation of a ing technique to obtain detailed at- 1992). The method consists of the acqui­ series of scintillation pattern images of a binary star; two turbulent layers can be distinguished clearly. mospheric turbulence profiles with sition of a large number of images with From the 2D autocorrelation, the structure constant 2 height, has been designed, developed very short exposure time (typically from of the refractive index with height, Cn (h), can be and tested by the Instituto de Astro- 1 to 3 ms, depending on the object and derived. The second to the sixth frames (left to right, física de Canarias. The instrument was the desired signal-to-noise ratio) of scin­ top to bottom) show the cross-correlations between two scintillation pattern images: cross-correlations developed to match the requirements tillation patterns produced by a double between an image and the ensuing correlation image of the ESO VLT Auxiliary Telescopes, star. The average autocorrelation function (upper centre), the second consecutive image (upper within the framework of the European computed from these images shows a right), and so on (bottom row). From these 2D cross- Extremely Large Telescope site charac- linear sequence of peaks corresponding correlations, wind velocity, V(h), can be inferred. terisation project. Commissioning at to the different turbulent layers. The dis­ Paranal was successfully carried out in tance between each peak and the centre November 2007. This upgraded ver­- gives information on the height of the atmospheric turbulence, in particular the 2 sion of the original instrument, presently ­turbulent layer (see example in Figure 1). knowledge of Cn (h) (the structure con­ working at the Roque de los Mucha- stant of the atmospheric refractive index chos Observatory, allows g-SCIDAR Initially, the classical SCIDAR was un- with height) and the wind profile (hori­ turbulence profiles to be obtained able to sample the layers closest to the zontal velocity of the layers) with a vertical in real time, a novel achievement in site ground. However a smart modification resolution better than 500 m. Many es- testing and also a crucial tool for the of the technique (Fuchs, Tallon & Vernin, sential parameters such as seeing (e), optimum design and operation of Adap- 1998) consisted in placing the analysis Fried’s parameter (r0), coherence lengths tative Optics and Multi-Conjugate plane not in the pupil plane but in a con­ and time of the wave fronts, isoplanatic

Adaptive Optics systems. jugated plane located a few km below the angles (q0), etc. can be computed from former. This development thus allowed g-SCIDAR data. The wind speed and the measurement of the turbulence inten­ direction with height V(h) can be retrieved The SCIDAR technique sity from ground to about 25 km height. by analysing the 2D cross-correlation This version of SCIDAR is known as gen­ functions from consecutive mean normal­ SCIDAR, SCIntillation Detection And eralised-SCIDAR (g-SCIDAR). ised images (see Figure 1). Ranging, has proved to be the most effi­ cient and reliable technique to accurately In practice, the implementation of such a measure the optical vertical structure of technique requires a minimum telescope Cute-SCIDAR since 2002 at the the atmospheric turbulence strength from diameter of approximately 1 m. So, Canary Islands ground level. The concept (Vernin & ­performing routine measurements using ­Roddier, 1973) and technique come from g-SCIDAR at a particular observatory Since 2002 campaigns have been car- the original one developed since the requires the use of significant resources. ried out by the IAC staff (Fuensalida et al., 80’s by Jean Vernin, Max Azouit and col­ However, g-SCIDAR provides extremely 2004a; Fuensalida et al., 2004b, laborators at Nice University (Vernin & valuable information regarding the optical ­Fuensalida et al., 2007) at their observa­

The Messenger 132 – June 2008 29 Telescopes and Instrumentation Vázquez Ramió H. et al., Cute-SCIDAR at Paranal for E-ELT Site Characterisation

tories: the Observatorio del Teide (OT) on Tenerife island and the Observatorio del Roque de los Muchachos (ORM) on La Palma island, both in the Canary Islands. In order to perform routine observations, two g-SCIDAR instruments were designed and manufactured to fit the particular specifications of the tele­ scopes which had to house them. They were Telescopio Carlos Sánchez (TCS) at the OT with 1.5 m diameter, and the Jacobus Kapteyn Telescope (JKT) be- longing to the Isaac Newton Group of Tele­scopes at the ORM with 1 m aper­ ture. Both systems implement the g-SCIDAR technique and include remote operation with facilities for conjugated plane positioning, spatial (X, Y) posi- tioning (centreing), a rotating system to adjust the direction of the pixel grid to the observed binary axis, etc. The remotely operated instrument is called cute-SCIDAR (c-SCIDAR).

The high resource cost entailed by the tated with minimal effort in the dome. Figure 2. Snapshot of the c-SCIDAR/Paranal GUI. monitoring of the turbulence with quite The instrument, based in the original The image on the left shows the scintillation pattern of a binary star. The normalised ­autocorrelation high resolution justifies the development g-SCIDAR concept of the Nice University, ­function can be seen in the middle frame, while the of an instrument with few constraints. was conceived to work in the coudé right panel shows a cut of the autocorrelation along The plans for a long campaign of meas­ focus of one of the 1.8-m Auxilliary Tele­ the binary axis. urements of the vertical structure of the scopes (ATs) of the VLT. The coudé focus turbulence in the ORM and OT observa­ is available in the focal station through – The instrument has its own cooling tories has encouraged us to build an the Upper Relay Optics Structure (UROS), ­s y s t e m . instrument with high performance and which becomes the interface between – Power supplies of the different systems minimal operational overheads. With the AT and c-SCIDAR (see Figure 3). are remotely controlled. this experience, we have been able – Operation and data acquisition is fully to develop a new version for the Paranal The main features of c-SCIDAR/Paranal remote by means of a user-friendly Observatory, within the European Ex- can be summarised as follows: Graphical User Interface (GUI). tremely Large Telescope Design Study – Mechanical and electronic matching to – Reduction of raw data is performed at (Contract 011863 with the European the UROS/AT interface. a rate that is higher than that of the Commission) which was supported by the European Community (Framework Programme 6, E-ELT Design Study).

C-SCIDAR at the Paranal Observatory

The c-SCIDAR/Paranal is a fully automat­- ic instrument. This means a complete automation of both displacement of opti­ cal elements and rotation of the instru­ ment itself. These movements are con­ trolled by a user-friendly interface (Figure 2). Moreover, a custom-made software package performs fast data acquisition and processing, which can provide the turbulence profiles in real time, with and without the turbulence contribution of Figure 3. Left: The cute-SCIDAR/Paranal attached the dome. As a consequence, alignment to the AT4 crane, during the November 2007 com­ and observation procedures are facili­ missioning. Upper: The original mechanical design of the instrument.

30 The Messenger 132 – June 2008 2 –2/3 ε = 0�970 θ0 = 2�222 log10 [Cn (m )] C-SCIDAR Paranal at 07/11/13 Current Observation observations, so allowing the profiling < >= 0 974 < > = 1 803 = 0 970 = 2 222 ε � θ0 � ε � θ0 �

Selected 08:01:21 U.T. –35–32 –28–25 –21–18 –14 Current 08:01:21 U.T. of the optical vertical turbulence in real 25 25 25

time (see Figure 4). –2 –24 8 –22 –286 –2–28 0 –224 20 20 –1 20–2 20 – –18 These design features lead to a high tem­ –18 –18 poral efficiency during the observing 15 15 15 campaign as well as providing an essen­ –2–108 tial tool in order to optimise the efficien­cy 10 10 10 of Adaptive Optics (AO) and Multi-Con­ Including Dome Turbulence Altitude above sea level (km) Altitude above sea level (km) Altitude above sea level (km) jugate Adaptive Optics (MCAO) systems. –18 5 5 –18 –1–8202 5 –26–2––2248 –242 –16 –1–2–1608 –16 Regarding the c-SCIDAR mechanisms, 0 0 0 –24–22 –20 –18 –16–14 01:00 02:0003:00 04:00 05:0006:00 07:00 08:00 –24–22 –20–18 –16–14 the camera is attached to three movable log [C2 (m–2/3)] U.T. (h) log [C2 (m–2/3)] 10 n 10 n stages which allow its movement along 25 25 25 28 –2 – –2 –20 X, Y and Z directions. The Z axis is em- 2 6 –208–2 4 4 20 20 –1 –2–22 20 8 –18 ployed both to determine the position of –1 the pupil plane and the focus (a single star allows the state of collimation of the 15 15 15 beam to be easily verified), but is main- –20–18 ly used to fix the conjugated plane where 10 10 10 Excluding Dome Turbulence Altitude above sea level (km) Altitude above sea level (km) the observations will take place. The X –18 Altitude above sea level (km) 5 5 0 –2–2024 5 –2 –6–2428 and Y direction stages are devoted to the –16 –24 –1–288 –2–22–0–1816 centring of the camera in the XY plane, –16 0 0 0 –24–22 –20 –18 –16 –14 01:00 02:00 03:00 04:0005:00 06:0007:00 08:00 –24 –22 –20 –18 –16–14 correcting small displacements in the log [C2 (m–2/3)] U.T. (h) log [C2 (m–2/3)] observation plane produced by flexure. 10 n 10 n The maximum range in the X and Y direc­ runs were planned to be performed for Figure 4. Output in real time of the profiles during an actual observing night. The central part is a repre­ tions is 25 mm, whilst in Z it is 100 mm. the duration of the FP6 contract. Actually 2 sentation of Cn (h). The contour plots are updated in An iris mechanism – an adjustable aper­ they took place just after the commis­ real time during the observation. The upper contours ture diaphragm placed in the focal plane – sioning period during a week in Nov- represent turbulence intensity with dome seeing facilitates the centring of the pupil image ember and later, during 10 nights in De- included, while the lower panel shows the same but of the double star onto the camera field cember. No new campaigns have been excluding dome turbulence (the white vertical gaps are associated with a change of object). The left and of view; the M6 mirror of the AT also plays carried out since then due to the lack of a right columns of the panel show individual vertical an important role in this particular proce­ free UROS (since the one initially devoted profiles: green is the average profile, navy corre­ dure. Finally, a rotator mechanism allows to SCIDAR was re-assigned to PRIMA). sponds to the last profile, and red to the particular the rotation of the instrument as a whole profile chosen with the cursor. in a range from 0˚ to 270˚, thus permitting the orientation of the binary star axis with References Fuensalida, J. J., Chueca, S., Delgado, J. M., et al. the array of the CCD camera. 2004b, in Advancements in Adaptive Optics, Fuchs, A., Tallon, M. & Vernin, J. 1998, PASP, 110, 86 eds. D. Bonaccini Calia, B. L. Ellerbroek and Fuensalida, J. J., Delgado, J. M., García-Lorenzo, B., R. Ragazzoni, Proc. SPIE, 5490, 749 All the observations and data analysis et al. 2004a, in Second Backaskog Workshop on Fuensalida, J. J., García-Lorenzo, B., Delgado, J. M., procedures applied to this upgraded ver­ Extremely Large Telescopes, eds. A. L. Ardeberg et al. 2007, Rev. Mex. Astron. Astrof., 31, 86 sion are the result of the development and T. Andersen, Proc. SPIE, 5382, 643 Vernin, J. & Roddier, F. 1973, J. Opt. Soc. Am., 64, 270 work carried out during the last few years Vernin, J. & Azouit, M. 1983, J. Opt. (Paris), 14, 131 by the IAC with the previous instruments Vernin, J. & Muñoz-Tuñón, C. 1992, A&A, 257, 811 at the Canaries Observatories. ESO will now operate the Paranal instrument and take care of the measurements while the IAC SCIDAR team will continue col­ laborating with ESO, within the FP6 Site Character­isation WP, on the data valida­ tion and analysis.

Present status Figure 5. Picture taken at the moment when cute-SCIDAR/Paranal Cute-SCIDAR/Paranal was successfully was providing real-time commissioned during November 2007 profiles for the first time by the IAC team with the collaboration of during the scientific the Paranal staff. In principle, regular long commissioning in No- vember 2007.

The Messenger 132 – June 2008 31 Astronomical Science

An early VLT UT1 ­colour image made from VLT Test Camera exposures in B, V and R filters of the polar disc galaxy NGC 4650A (see ESO Press Photo 19/98).

32 The Messenger 132 – June 2008 Astronomical Science

The Antares Emission Nebula and Mass Loss of a Sco A

Dieter Reimers, Hans-Jürgen Hagen, Antares sible a 2-D mapping of the nebula with Robert Baade, Kilian Braun A B long-slit spectroscopy. We used UVES (all Hamburger Sternwarte, Universität with a 0.4? slit and a resolution of 80 000 Hamburg, Germany) 2.7� and covered the nebula with 23 long-slit positions (Figure 1). Exposure times were between 50 and 100 s (the Antares neb­ The Antares nebula has been known as ula is bright!); the typical seeing was 0.6? a peculiar [Fe ii] emission nebula, ap- which means that the angular resolution parently without normal H ii region lines. corresponds roughly to the slit steps as Long-slit VLT/UVES mapping shows shown in Figure 1. that it is an H ii region 3? in size around the B type star a Sco B, with a Balmer Quite unexpected was that all spectra – line recombination spectrum and [N ii] even 10 ? from the M supergiant – are lines, but no [O ii] and [O iii]. The reason completely corrupted by scattered light for the non-visibility of [O ii] is the low from the M supergiant. This was a sur­ N electron temperature of 4 900 K, while prise, also to the UVES team at ESO. ESO [Nii] is seen because the nitrogen abun- finally made a test placing the UVES slit dance is enhanced by a factor of three 10 ? from a bright star – with the same W due to the CNO cycle. We derive a result as in our spectra. Apparently, light –6 mass-loss rate of 1.05 ± 0.3 × 10 MA/yr from the bright star is scattered by the slit for the M supergiant a Sco A. The [Fe ii] Figure 1. Geometry of the Antares system together jaws back to the slit viewing camera and lines seem to come mainly from the with the UVES spectrograph slit sizes and positions from there again into the spectrograph shown to scale. edges of the H ii region. slit. This should be a warning for anybody using UVES on faint targets close to bright UVES/VLT spectra, the Antares nebula sources, e.g. a disc, around a bright star. An iron rich nebula? puzzle could be solved. Did this mean that our spectra were use­ The story of the Antares nebula began in The most extensive previous study was less? It meant that, due to the ubiquitous 1937 with the finding of O. C. Wilson and that by Swings & Preston (1978) based on scattered light, no general background R. F. Sanford at the Mount Wilson Ob- high-resolution long-slit photographic reduction was possible and no absolute servatory that the spectrum of the B-type spectra taken with the Mt. Wilson 100? line fluxes could be deduced. Data reduc­ companion of Antares, itself an M super­ and Palomar 200? telescopes. They found tion required an enormous load of extra giant, showed forbidden emission lines that the ‘[Fe ii] rich nebula’ is strong roughly work. In brief, the scaled M star spectrum of Fe ii. Later Otto Struve showed that the 3.5? around the B star and is surrounded was used as a background template. [Fe ii] lines extend ~ 2? beyond the see- by a zone of weaker lines which may ex- The template was fitted to the spectrum – ing disc of the B star. Struve & Zebergs tend in a NW-SE direction up to 15?. How- allowing for an offset and a scaling – (1962) describe extensively the Antares ever, they neither observed Balmer re- ­outside a region of ± 30 km/s of each de- nebula and conclude: “It is strange that combination lines nor any classical H ii tected emission line and was finally the nebulosity around the B type com­ region lines from ions like O ii, O iii, S ii, and subtracted from the data. ponent shows only emission lines of iron N ii. Therefore the nature of the Antares and silicon, but not those of hydrogen. nebula could not be understood. In a first The final results after this elaborate data The enormous abundance of hydrogen in quantitative study of the Antares system reduction – each of the roughly 90 de- all known gaseous nebulae and the con­ it could be shown that the B star creates tected emission lines had to be treated ditions of excitation and ionization result­ an H ii region within the wind of a Sco A individually in each of the spectra – are ing from the radiation of a B type star and that the [Fe ii] lines must be formed in 2-D brightness distributions (location on would render it almost inexplicable for a this H ii region (Kudritzki & Reimers, 1978). the slit versus velocity) as a function of gas of normal composition to show only Later the H ii region was detected as an the location relative to the M supergiant, the iron and silicon lines in emission. optically thin radio emitter with a diameter as shown for the Ha line in Figure 2 and This gave rise to the hypothesis that the of ~ 3? (Hjellming & Newell, 1983). for [Fe ii] 4 814.55 Å in Figure 3. material in the vicinity of Antares is metal rich, in turn leading to the supposition that the envelope may be composed of UVES 2-D spectroscopy A peculiar H ii region? solid substances such as meteors that have become vaporized and are excited With the construction and operation of The main puzzle of the Antares Nebula by the radiation of the hot B star. This UVES at the VLT it was obvious that pro- has been resolved by our UVES data. The hypothesis is admittedly improbable and gress in our understanding of the kine­ Balmer recombination lines expected may have to be abandoned in the light matics of the Antares nebula should be for an H ii region: Ha, Hb ... up to H10 are of future work.” We may add here that the possible with its high spectral resolution present, and their geometrical extent mystery has lasted 45 years until, with and high pointing accuracy, making pos­ on the sky is virtually identical to that of

The Messenger 132 – June 2008 33 Astronomical Science Reimers D. et al., The Antares Emission Nebula and Mass Loss of a Sco A

0.9� 1.4� 1.9� 2.4� 2.9� 0.9� 1.4� 1.9� 2.4� 2.9�

3.4� 3.9� 4.4� 4.9� 5.4� 3.4� 3.9� 4.4� 4.9� 5.4�

10

8 8 ) ) � 6 � 6

Pos. ( 4 Pos. ( 4

2 2

0 30 0 0 30 –20 0 –40 –40 –20 Velocity (km/s) Velocity (km/s)

5.9� 6.4� 6.9� 7.4� 7.9� 5.9� 6.4� 6.9� 7.4� 7.9�

Figure 2. Ha 2-D brightness distributions (location Figure 3. [Fe ii] 4814.55 Å 2-D brightness distribu­ on the slit versus velocity) as a function of spectro­ tions as a function of spectrograph slit position (see graph slit position relative to a Sco A. Offsets from caption of Figure 2). Notice the double structure the position of a Sco A are shown in arcsec. Notice is probably formed by the front (blueshifted) and rear that due to the M star wind expansion, the velocity (redshifted) edges of the H ii region carried by the coordinate corresponds to the spatial depth (per­ wind to large distances from the system. pendicular to the plane of the sky). The density in the plots has been rescaled in order to provide maxi­ mum visibility. The true line fluxes vary by a factor of 150 between 1.9? and 7.9?.

the radio emission seen with the VLA normally prominent in H ii region spectra regions, are not? There are two reasons:

(Figure 4). So why have previous observa­ like [O iii] 4959/5 007 Å, [O ii] 3726/3729 a low electron temperature Te and an en- tions not shown the hydrogen lines? Å, [N ii] 6 583/6548 Å and [S ii] 6716/6731 hanced N/O ratio. At first, the electron

The reason is probably that the strongest Å had not been detected. Our UVES temperature Te must be so low that the lines Ha and Hb suffered, in the Mt. Wil­ spectra allow a more critical assessment [O ii] lines are not excited and below the son and Mt. Palomar photographic spec­ than earlier photographic spectra. The an- detection limit. We have modelled the tra, from seeing-dominated contamination swer is that we do see faint [N ii] 6 583 Å H ii region created by a Sco B in the wind by the M supergiant and the signal-to- and 6 548 Å lines, and that none of the of the M supergiant using the Cloudy noise of the photographic spectra was other lines is present. [N ii] 6 583 Å follows code (version 07.02.00, last described by never sufficient to enable an efficient closely the Ha distribution on the sky ­Ferland et al., 1998). Since the B star, with background subtraction. shown in Figure 2. Since it is close to Ha, an effective temperature of 18 200 K, is we can measure the Ha/[Nii] 6 583.4 Å relatively cool, the resulting electron tem­ The strongest lines are of [Fe ii] such as ratio as a function of the location in the perature is below 5 000 K which does not 4287.4 Å, 4 359.34 Å and 4814.55 Å. nebula. Close to the B star – in the mid­ allow [O iii] to exist and predicts [O ii]/Ha Altogether we have identified some 90 dle of the H ii region – Ha/[Nii] ≈ 3.5 while below our detection limit. But the same emission lines, besides [Fe ii] a few [Ni ii] 3? west of B, at the outer edge of the H ii model would also predict [N ii] below our and several strong allowed Fe ii lines like region, it is ~ 10. detection limit! The solution to this prob­ 3177.53 Å and 4 923.9/5 018.4/5169.0 Å lem is that Antares must have CNO-proc­ (see below). Beside the Si ii lines 3 856 For [O ii] we can give an upper limit: we essed material in its atmosphere and and 3862 Å we have detected further S iii have detected the Balmer line series up wind. Indeed, it has been shown by ­Harris lines around 5050 Å and at 6 347/6371 Å to H10, but H11 (close to [O ii] 3726/3729) & Lambert (1984) that in the atmosphere (for details and a line list cf. Reimers et was not visible. Thus, the H10 intensity of Antares 13 C and 17O are enhanced, al., 2008). as predicted by recombination theory, a clear indication of CNO cycle material. can be regarded as an upper limit to [O ii] Unfortunately there is no direct measure­ In all previous investigations of the which yields [O ii]/Ha < 0.017 for 3726 Å. ment of the N abundance (or N/O). Ty­- Antares nebula the question remained So why is [N ii] present, while the lines pical values for the N enhancement in open why the ‘classical’ emission lines of [O ii] and [O iii], usually stronger in H ii M supergiants of comparable luminos­-

34 The Messenger 132 – June 2008 Figure 4. Comparison of the distribu­ shows that at present the B star moves –26˚19�19� tion of Ha emission with radio free-free nearly perpendicularly into the plane emission (Hjellming & Newell, 1983) of the sky (Reimers et al., 2008) which, 20� (blue). Dashed red lines represent half, fourth, and tenth of the central Ha combined with wind expansion, pro­ emission flux. 21� duces a cometary structure (cf. Fig- ure 5). 22� – The UVES observations with 45˚ slit 23� position (Figure 1) confirm what Swings & Preston (1978) had seen, namely 24� that faint [Fe ii] emission is seen all along Declination (1950.0) the slit, i.e. in the neutral M star wind. 25� The explanation comes from the obser­ vation that one of the allowed lines, 26� Fe ii 5169 Å, appears both in the neutral 16 26m20.2 20.0 19.8 wind (position 0.9? from the M star) Right Ascension (1950.0) and in the H ii region. Apparently one channel for the excitation of the forbid­ ity are [N/H] = 0.6 (logarithmic abun­ has also been observed close to the den [Fe ii] lines is line scattering of dance ratio relative to solar), while oxygen ionisation front (Bautista et al., 1994). B star photons in the strong UV reso­ is slightly reduced, [O/H] = – 0.1. Our best nance lines, which was first seen with value for the nitrogen abundance de- – In addition to emission from the ionisa­ IUE (Hagen et al., 1987). One of the termined independently from a fit of the tion fronts there is apparently a further strong UV resonance (scattering) lines Cloudy models to observed [N ii]/Ha component (cf. Figure 3, 4? to 6? offset) in the UV spectrum of a Sco B is the ­values is [N/H] = 0.52 ± 0.1 with [O/H] ≤ in the centre of the H ii region. This is Fe ii UV mult. 3 line at 2 344 Å, which – 0.05 which is fully consistent with the again consistent with our Cloudy simu­ shows a P Cyg type profile. In the case expectations. lations which show such a further of the 2344 Å line, a second downward ­max­imum. We notice, however, that the channel exists via the Fe ii lines 4 923, Last but not least: the same Cloudy ‘central’ Feii emission varies strong- 5 018, and 5169 Å so that part of the ­models with the above mentioned abun­ ly with slit position which may have its dances show that metal line cooling ­origin in a time-variable (episodic) Figure 5. ‘Look back’ contours (solid lines) of H ii of the H ii region is dominated by [N ii] and supergiant wind. There is independent region borders in a plane perpendicular to the plane collisionally excited [Feii]. This is at least evidence, from both IR inter­ferometric of the sky caused by the combination of wind ex- part of the explanation for the strong [Fe ii] imaging of the immediate surrounding pansion with orbital motion of a Sco B relative to spectrum of the Antares nebula. of Antares and from the multiple com­ a Sco A. Contours are shown for present and previ­ ponent structure of CS absorption lines ous phases (–150 yrs to –450 yrs; 150 years being the wind travel time for the projected distance be- seen in HST spectra of a Sco B (Baade tween A and B). This is a qualitative model for the [Fe ii] emission & Reimers, 2007), for a time-variable cometary-like structure of the [Fe ii] emission regions. wind. The comparison of the distribution of the [Fe ii] emission in position and velocity – Emission is clearly seen outside of the space with Ha (Figures 2 and 3) shows H ii region: beyond 5.9? west of A, the distinct differences: [Fe ii] emission becomes more extended 0y and more structured. In velocity space −150y – The [Fe ii] emission is not smoothly dis­ the [Fe ii] emission moves in the mean −300y –1 tributed like Ha and [N ii] but is appar­ from 4 km s 1.9 ? west of A through −450y ently concentrated on the edges – the 3 km s–1 at B to 0 km s–1 5.9? west of A ionisation shock fronts – of the H ii re- and ~ – 5.5 km s–1 at 9.9? west of A. gion. The [Fe ii] emission thus gives rise to a ring-like structure (extending up Apparently we start to see here time- to ~ 6? from Antares outside the H ii re- dependent effects: the M supergiant gion itself), which ends roughly at 6?, wind carries the structure imprinted by thus making a double structure. This the H ii region (‘shock fronts’) to large ring-like and double-peak shape are distances from the system outside the apparent from the front and rear side of H ii region, where hydrogen is again the H ii region respectively, where the neutral. In addition, the systematic shift red component (rear side) is always in velocity can be explained by a com­ stronger. We notice in passing that the bination of B star orbital motion with occurrence of [Fe ii] in the Orion Nebula wind expansion. An analysis of the orbit

The Messenger 132 – June 2008 35 Astronomical Science Reimers D. et al., The Antares Emission Nebula and Mass Loss of a Sco A

downward cascade is via these lines H ii region shock fronts – which is cer­ fers from the episodic nature of mass and this is what we observe – Fe ii tainly an oversimplification. The geometry, loss (multicomponent absorption) and 5169 Å in emission. This channel popu­ i.e. the location of the B star and its from the observation that dust depletion lates the upper level of the strongest H ii region relative to the plane of the sky onto grains is important (Baade & Reim­ [Fe ii] lines 4 287 Å and 4 359 Å. In con­ at the M supergiant, has been deter­ ers, 2007). clusion, we have identified in detail mined using the Ha and [Fe ii] velocities from IUE and UVES observations the as 23˚ behind the plane of the sky. [Fe ii] excitation mechanism in the cold, References ­neutral M star wind far outside the H ii The best match of the Cloudy models Baade, R. & Reimers, D. 2007, A&A, 474, 229 region. with the observed Ha intensity distribu­ Bautista, M. A., Pradhan, A. K. & Osterbrock, D. E. tion (Figures 2 and 4) yields a mass-loss 1994, ApJ, 432, L135 –6 Ferland, G. J., Korista, K. T., Verner, D. A., et al. rate of 1.05 × 10 MA/yr with an uncer­ Mass loss of Sco A tainty of ± 30 %. This is a mean value over 1998, PASP, 110, 761 a Hagen, H.-J., Hempe, K. & Reimers, D. 1987, the crossing time of the wind through the A&A, 184, 256 The number of Lyman continuum pho­ H ii region of roughly 150 yrs. We believe Harris, M. J. & Lambert, D. L. 1984, ApJ, 281, 739 tons and the wind density (mass-loss that the new value for the mass-loss rate Hjellming, R. M. & Newell, R. T. 1983, ApJ, 275, 704 rate) determine the shape (size) of the is more reliable than (our own) previous Kudritzki, R. & Reimers, D. 1978, A&A, 70, 227 Reimers, D., Hagen, H.-J., Baade, R., et al. 2008, H ii region. At this time we have per­ measurements, mainly because the use A&A, submitted formed only static H ii region model calcu­ of circumstellar absorption lines in the B Struve, O. & Zebergs, V. 1962, Astronomy of the 20th lations assuming that the density struc­ star spectrum, formed in the vast circum­ Century, (New York: MacMillan Comp.), 303 ture is not grossly disturbed by the stellar envelope of the M supergiant, suf­ Swings, J. P. & Preston, G. W. 1978, ApJ, 220, 883

Another early VLT image showing the high ionisation bipolar planetary nebula NGC 6302. This colour pic­ ture is a composite of three VLT UT1 Test Camera exposures through B, V and R filters, taken in June 1998. The extremely hot (~ 200000 K) central star is hidden within the slender wisp of dust at the core of the nebula.

36 The Messenger 132 – June 2008 Astronomical Science

SINFONI Observations of Comet-shaped Knots in the Planetary Nebula NGC 7293 (the Helix Nebula)

Mikako Matsuura1, 2 Cometary knots in the planetary nebula molecular lines are not yet known. In par­ 3 Angela Speck NGC 7293 ticular, the H2 line excitation mechanism Michael Smith 4 of PNe in general is still a subject of dis­ Albert Zijlstra 5 The Helix Nebula (NGC 7293; Figure 1), pute and UV excitation and shock excita­ Krispian Lowe 6 located at 219 pc (Harris et al., 2007), tion have both been proposed. Serena Viti 2 is one of the closest planetary nebulae Matt Redman7 (PNe). The diameter of the entire nebula is Planetary nebulae are the late stages of Christopher Wareing 8 approximately a quarter of the size of the stellar evolution for low- and interme­ 5 Eric Lagadec the full moon. This proximity enables a diate-mass stars (1–8 MA on the main study of the detailed structure inside the sequence). The Sun is expected to reach nebula. The most interesting feature in this stage in about 5 billion years. The cir­ 1 National Astronomical Observatory of the Helix Nebula is its knots, which have cumstellar shell was produced by mass- Japan, Tokyo, Japan a typical size of 0.5–3 arcsec at their loss processes during the previous evo­ 2 Department of Physics and Astronomy, heads and are accompanied by tails up lutionary stage, the asymptotic giant University College London, United King­ to 15 arcsec long (O’Dell and Handron branch (AGB). As the central star evolves dom 1996; Figure 1). All of the knots have from the AGB towards the PN phase, 3 Physics and Astronomy, University of bright tips facing the central star and the the effective temperature increases, and Missouri, Columbia, USA tails extend in the opposite direction the circumstellar material in the nebula is 4 Centre for Astrophysics and Planetary away from the central star. The knots photo-ionised. PNe are regarded as a Science, School of Physical Sciences, were first discovered by Walter Baade in typical case of a photon-dominant region. The University of Kent, Canterbury, about 1940, according to Vorontsov- Moreover, a fast but low mass-loss rate United Kingdom Velyaminov (1968). The formation mecha­ stellar wind from the PN central star 5 School of Physics and Astronomy, Uni­ nism of these tails is not well understood: catches up with the slow but dense AGB versity of Manchester, United Kingdom the two most likely explanations are mass wind, and so the circumstellar envelopes 6 Science and Technology Research Cen­ injection from cores followed by hydrody­ tre, University of Hertfordshire, ­Hatfield, namic processes creating a tail, or photo- Figure 1. The optical image of the Helix Nebula (top) United Kingdom ionisation of an optically thick globule formed from images in a 502 nm filter ([O iii]) and 7 Department of Physics, National Univer­ creating a shadow. Furthermore, ionised 658 nm filter (Ha and [N ii]) is shown. The square sity of Ireland Galway, Republic of Ire­ lines, hydrogen recombination lines, and region is enlarged in the lower panel to show the land molecular emission (H and CO) have knots in the inner region of the Helix Nebula. 2 Adopted from images taken with HST and NOAO. 8 School of Mathematics, University of been detected from these knots. How­ (Credit: NASA, NOAO, ESA, M. Meixner and T. A. Leeds, United Kingdom ever, the excitation mechanisms of the Rector)

One of the most interesting characteris- tics of the planetary nebula NGC 7293 (the Helix Nebula) is its comet-shaped knots. We have observed one of the knots using the SINFONI imaging spec- trometer on the VLT with adaptive op- tics. The spectra are analysed to obtain the spatial variation of molecular hydro- gen line intensities within the knot. The images clearly show the detailed struc- ture, which resembles a tadpole in shape, suggesting that hydrodynamic flows around the knot core create a pressure gradient behind the core. The three-dimensional spectra reveal that the excitation temperature is uniform at approximately 1800 K within the knot. The SINFONI observations help to determine the H2 excitation mechanism in planetary nebulae, as well as the importance of hydrodynamics in shap- ing the knots.

The Messenger 132 – June 2008 37 Astronomical Science Matsuura M. et al., SINFONI Observations of Comet-shaped Knots in NGC 7293

of PNe are a good test case for hydrody­ namic simulations. (a)

The power of SINFONI AO Guide Star Integral field spectrometers allow the simultaneous measurements of an image and many spectra on an individual pixel basis, and so these instruments are ideal for investigating spatial variation of line (b) intensities, and thus line excitation mech­ anisms within nebulae (e.g. Tsamis et al., 2008). SINFONI is a near-infrared integral field spectrometer, covering the wave­ length range which contains molecular hydrogen rotational-vibrational lines around 2 microns. SINFONI can be sup­ ported by an adaptive optics (AO) sys- tem, which allows observations to be (c) taken with high spatial resolution. Thus it is an ideal instrument to investigate the structure of small-scale (a few arcsec) objects, such as knots in planetary nebu­ lae.

We used SINFONI to obtain 2 micron Figure 2. (a) Optical image showing the location of integral field spectra of a knot within the that spatially resolved H2 spectra have Helix Nebula (Matsuura et al., 2007). been obtained within a knot. The SIN­ the target and a nearby field star which was used for adaptive optics. (b) The SINFONI image of the There are many field stars inside this neb­ FONI data also provide line ratio maps, knot at 2.12 micron covering the H2 v = 1–0 S(1) line; ula, and we chose a knot close to one which gives a measure of the H2 excita­ (c) close-up of the crescent taken with SINFONI at of the field stars, which was used as a tion temperature. The line ratio maps ap- a scale of 100 milliarcsec per pixel but resampled to guide star for the AO system. The images 50 milliarcsec pixels. The image size is 4.2 arcsec by 3.9 arcsec. obtained with AO assistance achieve the highest angular resolution of any im- (a) SINFONI 2.12 micron H v = 1– 0 S(1) ages of the Helix Nebula, up to about 2 70 milliarcsec. Figure 2 shows the SIN­ FONI image of the knot in the Helix Neb­ ula. The knot was clearly resolved into an elongated head and two narrow tails. The overall shape resembles that of a tadpole. The brightest emission is found in a crescent within the head. The diam­ eter of the head is approximately 2.5 arc­ (b) HST F658N sec, while that of the tails is about 2.9 arc- [NII] 658.3 nm + Hα 656.3 nm sec. We found that the tails are brighter in H2 than in optical H-alpha+[N ii] emis­ sion (Figure 3). In the optical, almost only the crescent at the head is found and the tail is barely seen.

As an integral field spectrometer, SIN­ (c) HST F502N [O III] 500.7 nm FONI can provide a spectrum at every Figure 3. A comparison of SINFONI H2 single spatial pixel over the field. Figure 4 and optical images. The tails are much more obvious in the H line (a) than in shows representative spectra within the 2 the 658 nm image (b). The knot is knot obtained by the SINFONI instrument. found to be negative in 500.7 nm [O iii] Integral field spectroscopy enables the line (c), because the dust in the knot absorbs the background emission, spatial variation of the intensities of H2 lines to be studied. This is the first time while the surrounding area has diffuse [Oiii] emission unaffected by dust.

38 The Messenger 132 – June 2008 8 × 10 8 8 × 10 8

6 × 10 8 6 × 10 8 ) ) –1 –1 4 × 10 8 4 × 10 8 (Jy sr (Jy sr ν ν I I

2 × 10 8 2 × 10 8

0 0

2.02.1 2.22.3 2.4 2.02.1 2.22.3 2.4 Wavelength (µm) Wavelength (µm)

8 × 10 8 8 × 10 8

6 × 10 8 6 × 10 8 ) ) v = 1–0v = Q(2) 1–0v = Q(3) v = 2–1 S(1) v = 1–0v = S(0) v = 1–0v = S(1) v = 1–0v = S(2) –1 –1 4 × 10 8 4 × 10 8 (Jy sr (Jy sr ν ν I I

2 × 10 8 2 × 10 8 v = 1–0v = Q(1) v = 2–1 S(2) v = 1–0v = S(3)

0 0

2.02.1 2.22.3 2.4 2.02.1 2.22.3 2.4 Wavelength (µm) Wavelength (µm)

Figure 4 (above). SINFONI spectra of H2 lines, with Figure 5 (below). Line ratio maps, showing (a) the identification of transitions in the right bottom panel, rotational temperature and (b) the vibrational temper­ at different locations around the knot shown in the ature of H2 molecules. The excitation temperatures central image. appear to be uniform within the knot, outlined by a white line.

(a) (b) I2.03 micron v = 1–0 S(2)/I2.12 micron v = 1–0 S(1) I2.24 micron v = 2–1 S(1) /I2.12 micron v = 1–0 S(1) 0.20

2 × 0.8 2 × 5 10 5 10 –8 –8 0.15

4 0.6 4 Ratio Ratio 3 3 0.10 0.4

2 2 Distance (arcsec) Distance (arcsec) 2 × 2 × 10 10 0.05 –8 –8 0.2 1 1

0.0 0 0.0 0 012 3 4 5 0 1 2 3 4 5 Distance (arcsec) Distance (arcsec) pear to be uniform within the knot (Fig- Shaping of the knots indicate the involvement of hydrodynam­ ure 5). Using all of the H2 lines detected ics. The bright crescent is a bow shock at 2 microns (up to 12 lines), we derived The mechanism responsible for the for­ and the stellar wind from the central star an excitation temperature of 1800 K, mation and shaping of the knots has blows the material off, or alternatively and all of the intensities follow local ther­ been the subject of a long-term debate. radiation from the central star heats the modynamic equilibrium (LTE). The long tails of the tadpole-like knots core evaporating the gas which forms

The Messenger 132 – June 2008 39 Astronomical Science Matsuura M. et al., SINFONI Observations of Comet-shaped Knots in NGC 7293

a pony-tail pointing away from the central Stellar wind Core (not real size) star. The tail is narrower than the head, probably because of the pressure differ­ ence behind the head caused by the ­stellar wind (Figure 6). One of the best or models to reproduce the tadpole shape has been developed by Pitterd, Dyson, Molecules removed from the core or and their colleagues (e.g. Dyson et al., Photons Molecules could be formed by collision 2006). According to their model, the tad­ at the surface of the core pole shape can be produced if material is constantly removed from the core of a knot by the stellar wind, and if the velocity of the wind is about supersonic. Their models show that the velocity of the am- Stellar wind bient gas is between 26 and 38 km/s in the case of the Helix knots. Such a high expansion velocity component has been detected in the outer part of the Nebula (Walsh and Meaburn, 1987), but not yet in the inner part; in the inner part, only slower (10 km/s) winds have been Pressure from the stellar wind detected so far. The detection of high ve- locity components from the knotty region would be of further interest. Gas flow

The excitation mechanism of molecular hydrogen

The excitation mechanism of molecular hydrogen in PNe has been a long-term controversy. From the knots, CO mole­ cular emission has been detected but their upper level energy is only 6 K, much lower than that for H2 (typically from 6 000 to 8 000 K for the rotational-vibration lines at 2 microns). In order to reach the energy Within the choice of existing models and Figure 6. A schematic view of the formation of a knot of such an upper level and to acquire an their parameter ranges, C-type (continu­ in a planetary nebula by the effects of the stellar wind. excitation temperature of thousands of K, ous) shock models with an ambient gas a line excitation mech­anism should be velocity of 27 km/s (Burton et al., 1992) present. There are two major mechan­ can reproduce the measured H2 intensi­ isms proposed to excite rotational-vibra­ ties in the Helix Nebula. In contrast, UV tion lines of molecular hydrogen at radiation models can fit the observations, 2 microns: collisional and fluorescent ex- only if the UV flux is increased by a fac- References citation. For shock excitation, kinetic tor of 250 above that expected from the Burton, M. G., Hollenbach, D. J. & Tielens, energy is absorbed in increasing the central star. Within the current choice, A. G. G. M. 1992, ApJ, 399, 563 internal energy of the molecules, and the our observations favour shock excitation Dyson, J. E., Pittard, J. M., Meaburn, J., et al. 2006, A&A, 457, 561 H2 line intensities follow a thermal pop­ of H2 lines. ulation distribution. However UV radiation Harris, H. C., Dahn, C. C., Canzian, B., et al. 2007, AJ, 133, 631 in photon-dominant regions increases The non-detection of a shocked region in Matsuura, M., Speck, A. K., Smith, M. D., et al. the population of rotation-vibrationally the SINFONI image still remains a mys­ 2007, MNRAS, 382, 1447 Meixner, M., McCullough, P., Hartman, J., et al. excited states, and vibrationally excited tery: if the H2 lines are excited by shocks, molecules then decay by emitting pho­ the excitation temperature should be 2005, AJ, 130, 1784 O’Dell, C. R. & Handron, K. D. 1996, AJ, 111, 1630 tons in the near-infrared. The population highest at the tip of the tadpole, i.e., on Speck, A. K., Meixner, M., Fong, D., et al. 2002, of UV excited states are often detected the crescent. However, our SINFONI ob- AJ, 123, 346 in non-LTE in rotational-vibration lines, servations did not detect such a shocked Tsamis, Y. G., Walsh, J. R., Pequignot, D., et al. but in an intense UV field, and depending region (Figure 5). This could be because 2008, MNRAS, 355, in press Vorontsov-Velyaminov, B. A. 1968, IAU Symp., on the gas density, fluorescence can the scale of the shocked region is still too 34, 256 ­create a thermal population distribution. small to be resolved even with SINFONI. Walsh, J. R. & Meaburn, J. 1987, MNRAS, 224, 885

40 The Messenger 132 – June 2008 Astronomical Science

Hunting for the Building Blocks of Galaxies like our own Milky Way with FORS

Martin G. Haehnelt1 Searches for young galaxies terparts has usually been frustrated Michael Rauch 2 by the difficulty of detecting an extremely Andrew Bunker 3 The search for and discovery of young faint object (the DLA host) next to an ex- George Becker 2 galaxies at high redshift has involved a tremely bright object (the QSO). Searches Francine Marleau 4 number of unexpected twists and turns. (e.g. Warren et al., 2001, Christensen James Graham5 Early predictions of young galaxies shin­ et al., 2006) have so far produced only a Stefano Cristiani6 ing brightly in Lya line radiation (Partridge handful of confirmed detections of the Matt J. Jarvis 7 & Peebles, 1967) have not been borne underlying galaxies. Such efforts indi­ Cedric Lacey 8 out by reality. The first detections of an cated that DLA hosts at high redshift are Simon Morris 9 entire population of ordinary (i.e., non- generally drawn from the very faint end Celine Peroux10 AGN) high-redshift galaxies came from of the general galaxy population at high Huub Röttgering11 the observations of damped Lya systems redshift (Møller et al., 2002), giving sup­ Tom Theuns9 seen in absorption against background port to the idea that DLAS host galax- QSOs (e.g. Wolfe et al., 1986). Detections ies have rather low masses (Haehnelt, of substantial numbers of high-redshift Steinmetz & Rauch, 2000), albeit with a 1 Institute of Astronomy, Cambridge, galaxies in emission had to wait for an- considerable gas cross-section. United Kingdom other decade and larger telescopes, and 2 Observatories of the Carnegie Institu­ came to rely not on emission lines but on tion of Washington, Pasadena, USA broadband continuum (‘Lyman break’) A search for faint Lya emitters and 3 Anglo-Australian Observatory, Epping, features (e.g. Steidel & Hamilton, 1995). a surprising discovery Australia These searches yielded massively star 4 Spitzer Science Center, Caltech, forming galaxies where, ironically, the We report here on the results of an ultra- Pasadena, USA expected Lya emission was often highly deep, spectroscopic blind survey for 5 University of California, Berkeley, USA suppressed because of dust absorption. low-level Lya emission using FORS2 on 6 Osservatorio Astronomico di Trieste, With the advent of 10-m-class telescopes, the VLT (Large Programme 173.A-0440). INAF, Italy narrowband surveys for Lya line emis- The original motivation was to search 7 Centre for Astrophysics, Science & sion finally reached sufficient depth, dis­ for ­fluorescent Lya emission from the Technology Research Institute, Univer­ covering considerable numbers of gal­ optically thick part of the gaseous cosmic sity of Hertfordshire, Hatfield, United axies with large Lya equivalent widths web (Lyman Limit systems and DLAS), Kingdom (e.g. Cowie & Hu, 1998). The relation be- induced by the general UV background 8 Institute for Computational Cosmology, tween the galaxy populations selected by (Hogan & Weymann, 1987; Gould & Department of Physics, University of these three different methods has so far ­Weinberg, 1996). Line emission in re- Durham, United Kingdom remained obscure. Galaxies selected by sponse to recombinations caused by the 9 Department of Physics, University of Lya line emission (down to typical narrow- impinging UV photons would cause any Durham, United Kingdom band limiting fluxes of a few × 10–18 erg patches of optically thick gas to exhibit a 10 Observatoire Astronomique de s–1 cm–2), though similar in numbers to universal ‘glow’ of Lya photons. For ­Marseille-Provence, France Lyman break selected galaxies, appear this purpose we obtained a FORS2 spec­ 11 Leiden Observatory, the Netherlands different from these because of their much trum of a basically blank piece of sky larger line-to-continuum ratios. Both with the 7; × 2 ? slit exposed for 92 hours emitter populations appear more metal- (120 hours including overheads). We report results from our ultra-deep rich and have star-formation rates larger spectroscopic survey for low surface than compatible with the low metallicity The field contained a moderately bright brightness Lya emitters at redshift and low dust contents of damped Lya QSO and was observed during 2004– z ~ 3. A 92-hour-long exposure with the systems (DLAS). 2006 with the volume-phased holo­ ESO VLT FORS2 instrument has yielded graphic grism 1400 V on FORS2. The a sample of 27 faint line emitters with resulting 2-dimensional spectrum is fluxes of a few times 10–18 erg s–1 cm–2 DLAS and the general population of shown in Figure 1 with the spatial direc­ which we argue are likely to be domi- star-forming galaxies tion shown vertically and the spectral nated by Lya. The large comoving direction shown horizontally. The spec­ number density, the large covering fac- The key to a full understanding of the trum ranges from 4 457 to 5776 Å. De- tor, dN/dz ~ 0.2–1, and the spatially general population of galaxies at high spite the long exposure time we were extended surface brightness of the redshift, likely to be less actively star- able to reach the sky noise limit and the emission suggest that the emitters can forming and, at least according to the surface brightness detection limit for line be identified with the elusive host popu- CDM paradigm, far more numerous than photons of our spectrum is an unprece­ lation of damped Lya systems (DLAS) either of the two bright classes of objects, dented 8 × 10–20 erg cm–2 s–1 arcsec–2. and high column density Lyman limit must lie with the DLAS. Unfortunately, systems. The finding suggests that most DLA host galaxies have remained largely We had expected to detect about 30 op- Lyman limit systems and DLAS are part elusive at high redshift. The attempt to tically thick patches fluorescing at very of the same low-mass galaxies. identify individual DLA with galaxy coun­ low light levels in Lya with a median

The Messenger 132 – June 2008 41 Astronomical Science Haehnelt M. G. et al., Hunting for the Building Blocks of Galaxies with FORS

proaching the total space density of local

dwarf galaxies as faint as MR = –13. If the emission were instead due to [O ii] or [O iii], the corresponding space density would be larger than the space density of local dwarf galaxies by factors 6 and 100, re- spectively. From a statistical point of view, most of the 27 single-line emitters should thus indeed be Lya. This interpretation is supported by the typical asymmetric shape of many of the emitters and the fact that we have also detected the ex- pected number of [O ii] emission line dou­ blets.

A steeply rising faint end of the luminosity function of Lya emitters

Even though the inferred space densities are smallest if the line emission is identi­ fied as Lya, the resulting space density still implies a significant steepening of the luminosity function of Lya emitters below flux levels reached by previous surveys. In Figure 3 we compare the cumulative lu- minosity function inferred from our 27 line emitters (neglecting slit losses) with the luminosity function from published sur­ veys. Due to the spectroscopic nature of Figure 1. Two-dimensional spectrum obtained in Figure 2 shows a mosaic of the 27 single- our survey and the long exposure time, 92 hours of exposure time with FORS2 at the VLT. line emitters. Many emitters are consider­ we reach more than a factor 10 lower flux The line emitter candidates for H i Lya are enclosed by the numbered boxes. The dispersion direction is ably extended in wavelength and real levels. There is good agreement in the horizontal, with blue to the left and red to the right; space, suggesting the importance of overlap region at the bright end. Towards the spatial direction along the slit is vertical. The fig­ radiative transfer in shaping the appear­ fainter magnitudes the luminosity function ure is adapted from Rauch et al. (2008). ance of the objects and thus an identifi­ appears to steepen significantly. cation as Lya line. The detectable emis­ diameter of 5 arcsec. The expected large sion often extends to ‘radii’ as large as spatial extent meant that we could ac- 4 arcsec. Physical origin of the line emission cept observing time in periods of moder­ ate seeing for which there is substantially An identification of the emission as Lya less demand. What are the faint spatially extended raises the question of the potential emis­ line emitters? sion mechanisms. We will briefly consider However, as we will describe below, the­ three possibilities here: fluorescent (re-) oretical estimates of the UV background For the 27 single-line emitters – at least in emission of the meta-galactic UV back­ intensity had gone down during the pro- principle – [O ii], [O iii] and Lya are all ground; gas cooling; and emission due to ject, and so we were probably somewhat ­possible identifications. Obviously the dif­ the formation of (massive) stars. As al- short of the signal-to-noise ratio required ferent interpretations differ drastically in ready discussed, the original aim of our to detect the fluorescent (re-) emission the inferred range of redshift, luminosity project was to detect fluorescent emis­ of the meta-galactic UV background from and star formation and most crucially sion from optically thick regions. For this optically thick regions in a blank field. We in the inferred space density (see Table 1). purpose we further increased our sensi­ nevertheless found 27 single-line emitters tivity by stacking the individual spectra of on the slit, however with total fluxes typi­ In a publication to appear in the ApJ our emitters. In Figure 4 we compare cally a factor five to ten higher than our (Rauch et al., 2008), we argue in consid­ the result of this stacking analysis to our revised expectations for the signal from erable detail that most of the emitters are expectation for the fluorescent emission fluorescence alone. We also detected a likely to be Lya at redshift z ~ 3.2. Our (see Rauch et al. (2008) for more details). number of low-redshift line-emitting inter­ main argument concerns the inferred The points with error bars and open lopers by their [O ii], [O iii], and H i Balmer space densities. With an identification as squares show our measurements of the series emission. Lya, the inferred space density is ap- mean and median surface brightness

42 The Messenger 132 – June 2008 50 50 50 50 50 50 40 40 40 40 40 40 30 30 30 30 30 30 20 20 20 20 20 20 10 10 10 10 10 10 0 0 0 0 0 0 01020304050 01020304050 01020304050 01020304050 01020304050 01020304050 1 6 9 12 16 19

50 50 50 50 50 50 40 40 40 40 40 40 30 30 30 30 30 30 20 20 20 20 20 20 10 10 10 10 10 10 0 0 0 0 0 0 01020304050 01020304050 01020304050 01020304050 01020304050 01020304050 21 24 25 26 30 33

50 50 50 50 50 50 40 40 40 40 40 40 30 30 30 30 30 30 20 20 20 20 20 20 10 10 10 10 10 10 0 0 0 0 0 0 01020304050 01020304050 01020304050 01020304050 01020304050 01020304050 39 27 3 23 28 29

50 50 50 50 50 50 40 40 40 40 40 40 30 30 30 30 30 30 20 20 20 20 20 20 10 10 10 10 10 10 0 0 0 0 0 0 01020304050 01020304050 01020304050 01020304050 01020304050 01020304050 15 36 37 4 10 17

50 50 50 40 40 40 Figure 2. Spectra of individual line emitters (15.12? or 30 30 30 116 proper kpc wide in the spatial direction and about 2 266 km/s long in the spectral direction). The 20 20 20 areas within the turquoise contours have a flux den­ 10 10 10 sity greater than approximately 10–20 erg s–1 cm–2 Å. 0 0 0 01020304050 01020304050 01020304050 The first 12 spectra show a single central peak; the 18 20 38 next six show a clearly asymmetric red peak with a much weaker blue counter-peak; the following three either have a stronger blue than red peak (ID 15) or emission features blueward of an absorption line (36, 37); the remaining six spectra are unclassifiable. The figure is adapted from Rauch et al. (2008). as a function of angular distance from the principle, the Lya radiation could be pro­ centre of emission along the slit, respec­ duced by the cooling of gas in galactic with the observed high space density and tively. The dotted curves give the range haloes. However, as we argue in detail in the implied low masses of the underlying of the expected surface brightness for Rauch et al. (2008), this may be true for haloes. This leaves Lya radiation from the fluorescent (re-) emission of the meta- a few of our objects but not for the major­ centrally concentrated formation of (mas­ galactic UV background based on recent ity. The reason is that the observed Lya sive) stars, resonantly scattered in an measurements of photo-ionisation rate luminosity is too high to be consistent optically thick galactic halo, as the most of the Intergalactic Medium at z ~ 3. The predictions for the Lya fluorescence are a factor two to four lower than the meas­ [Oiii] [Oii] Lya ured surface brightness of our line emit­ Redshift 0–0.15 0.2–0.55 2.67–3.75 ters in the stacking analysis. [z] Luminosity 2 × 1036 3.7 × 10 38 7.9 × 1040 [h –2 erg s–1] –3 × 1038 –2 × 1040 –1.6 × 1042 The spectral line shapes and sizes of our 7 0 S t a r - f o r m a t i o n r a t e 5 × 10–3 7 × 10 –2 emitters suggest that the Lya photons –2 –1 [h7 0 MA yr ] –0.3 –1.5 Table 1. Properties of have been processed by radiative transfer Space density 9 0.5 3 × 10–2 line emitters for different 3 –3 through an optically thick medium. In [h7 0 Mpc ] possible identifications.

The Messenger 132 – June 2008 43 Astronomical Science Haehnelt M. G. et al., Hunting for the Building Blocks of Galaxies with FORS

promising remaining emission mecha­ –1 Figure 3. Observed cumulative lumi­ nosity function at z = 3.1 from Ouchi nism. ]

–3 et al. (2007; dashed curve), z = 2.9 –2 from van Breukelen et al. (2005; dash-

Mpc triple dotted curve) and our sample

Have we discovered the host galaxies 3 70 (solid curve, dotted curves represent of DLAS? 1s error contours). The dot-dashed –3 curves are theoretical predictions. From Rauch et al. (2008). As discussed above the difficulties in finding the host galaxies of DLAS, as well –4 The present study as theoretical models within the LCDM Ouchi et al. paradigm for structure formation, suggest van Breukelen et al. log (dN(>L)/dV) [h –5 that DLA host galaxies are fainter and Le Delliou et al. more numerous than typical Lyman break 021 34 galaxies. Unfortunately, absorption line log (L [10 40h–2 erg s–1]) studies only constrain the total incidence Lyα 70 rate, which depends on the product of space density and cross section for ab- Figure 4. Mean (points with error bars) 8 and median (open squares) surface

sorption. With our spectroscopic survey ) brightness measurements in units of we have measured the space density and –19 10 –19 erg cm–2 s–1 arcsec–2 for the the size of the objects. We can thus pre­ 6 combined surface brightness profiles, dict the expected rate of incidence for as a function of angular distance in absorption by the emission regions of our arcsecs from the centre of emission along the slit. The dotted curves give putative population of faint spatially ex- 4 the range of the expected surface tended Lya emitters. In Figure 5 we show brightness based on the photo-ionisa­ this incidence rate as a function of the tion rate of the z ~ 3 Intergalactic 2 measured ‘radius’ of our emitters. The Medium. The upper dotted curve is for a QSO type UV spectrum, the bottom cumulative rate of incidence is very simi­ Mean, median SB (10 curve for a spectrum where 50 % of lar to that of DLAS, suggesting that we 0 the flux is contributed by galaxies. The may indeed have discovered a substantial dashed curve is the 4s surface bright­ 1 234 567 part of the elusive population of DLA host ness detection threshold for individual Dist. along slit (arcsec) objects. From Rauch et al. (2008). galaxies.

0.8 Figure 5. Contribution of objects of The elusive continuum different sizes to the predicted rate of incidence per unit redshift, dN/dz for H i with (dotted line) and without The essential, but missing piece of evi­ 0.6 (solid line) correction for the extended dence in this puzzle is clearly the rest- sizes and our underestimating the frame UV continuum radiation of the ob- radius. The short vertical line on top of the uncorrected curve indicates the jects. A knowledge of the continuum 0.4 spatial resolution limit along the slit. would allow us to unambiguously identify From Rauch et al. (2008). each individual case as a high redshift H I ­galaxy. Knowledge of the continuum will 0.2 log (dN(>radius)/(dz)) also give us a more reliable measure of H I corrected the star-formation rate and provide con­ straints on the morphology of these 0.0 ­galaxies – it will tell us what these objects 0210 030 really are. Unfortunately, the expected Radius (phys. kpc) continuum emission is very faint. In Fig- ure 6 we compare the cumulative UV con- The next step most efficient way for testing this hypoth­ tinuum luminosity function of Lyman esis, and for constraining further the frac­ break galaxies in the Hubble Ultra-Deep The similarity of the space density of our tions of true Lya emitters and interlopers, Field (HUDF) with those predicted for our emitters to that of the Lyman break gal­ would be to repeat our ultra-deep spec­ line emitters assuming a rest-frame EW axy population at the faint end of the troscopic survey in the HUDF. This should of 70 Å. The space density of our line UV continuum luminosity function in the be considered a modest investment emitters is similar to those of the faintest HUDF is tantalising, but circumstantial, of (moderate seeing!) observing time in Lyman break galaxies in the HUDF evidence that these may be the same return for substantial progress in under­ ­(Bouwens et al., 2007). objects, once seen by their centrally con­ standing the formation of typical present- centrated continuum and once by day galaxies like our Milky Way. their spatially extended Lya emission. The

44 The Messenger 132 – June 2008 –1 Figure 6. Cumulative UV continuum References

] The present study luminosity functions of Lyman break –3 HUDF Bouwens et al. galaxies and the cumulative distribu­ Bouwens, R. J., Illingworth, G. D., Franx, M., et al. –2 Steidel et al. tion of our survey (solid line; dotted 2007, ApJ, 670, 929 Mpc lines are ±1s errors). The emitters Christensen, L., Wisotzki, L., Roth, M. M., et al. 3 70 are assumed to have a con­tinuum 2006, A&A, 468, 587 –3 mag­nitude predicted by their Lya line Cowie, L. L. & Hu, E. M. 1998, AJ, 115, 1319 flux assuming a rest-frame equiva­- Gould, A. & Weinberg, D. H. 1996, ApJ, 468, 462 lent width of 70 Å. From Rauch et al. Haehnelt, M. G., Steinmetz, M. & Rauch, M. 2000, –4 (2008). ApJ, 534, 594 Hogan, C. J. & Weymann, R. J. 1987, MNRAS, 225, 1 Møller, P., Warren, S. J., Fall, S. M., et al. 2002, ApJ, –5 574, 51

log (dN(

Colour-composite image of a triplet of galaxies which make up part of the Hickson Compact Group HCG 90. The galaxies in the image are NGC 7173 (north), 7174 (south-east) and 7176 (south-west); the image orientation is north up, east to the left and the size is about 5.3 arcminutes. The image is based on data obtained with VLT FORS1 with B, V, and R filters. NGC 7173 and 7176 are elliptical galaxies, while NGC 7174 is a spiral galaxy with a disturbed dust lane. See ESO PR Photo 02/08 for more details. Image processing by Henri Boffin (ESO).

The Messenger 132 – June 2008 45 Astronomical News thermal infrared portraits in front of the ESO stand. ESO the of front in portraits infrared thermal their displaying family A Lower: not-so-young. and young the to projects ESO explaining ­Kerber ­ and Liske Jochen Astronomers Upper: 7–11 2008. Germany, June Mannheim, at place took which event Science” “Explore the from Views Florian Florian

Photo: E.Janssen, ESO Astronomical News

News from the ESO Science Archive Facility

Nausicaa Delmotte (ESO) requester will be informed that they have The GOODS/VIMOS spectroscopy data N status (“Not available”). The request (version 1.0) was released in February will be closed and the user should simply 2008. It contains the results of the first Latest developments of the ESO archive try again after waiting for an appropriate half of the GOODS/VIMOS spectroscopic including timely access to proprie- time. campaign of the ESO/GOODS large tary data, a new science-oriented query ­programme 171.A-3045 (PI C. Cesarsky) form and new data releases are pre- Second, the one-year proprietary period using two different grisms (Low resolu- sented. for the data requested begins when tion Blue, 3500–6900 Å, and Medium the corresponding archive request is suc­ resolution Orange, 4 000–10 000 Å) cessfully completed (i.e. data files are between 2004 and 2006. 3 312 fully PI access to own proprietary data made available to the requester). This is reduced and calibrated spectra of 3121

consistent with the policy that whenever unique sources down to i775 (AB) magni­ As of 1 April 2008, Principal Investigators data are made available to the PI (e.g. tude of 25, along with a catalogue of (PIs) can access their own raw proprie­ through a DVD shipment), then the pro­ 2 000 redshifts, of which 985 are classi­ tary data at any time through the ESO prietary clock starts. fied ‘high quality’ (grade A), are being archive. This new feature is an upgrade of released. The 1-sigma redshift accuracies the current User Portal system released are ~ 300 km/s and ~ 200 km/s for the last year (see Tacconi-Garman 2007). To Science-oriented query form low- and the medium-resolution obser­ this end, the archive system was modi- vations, respectively. A full description of fied and the archive web interfaces were A new archive query form was released the survey can be found in Popesso et adapted to reflect this change. The re- in May 2008 as a common entry point to al., 2008. sults of archive web searches are now search among all the collections of both colour coded. Datasets for which the pro­ imaging and spectral ESO advanced data Version 1.1 of the GaBoDS WFI data prietary period is over are highlighted in products. See http://archive.eso.org/eso/ release (Hildebrandt et al., 2006) took green and are publicly available. Datasets eso_archive_adp.html. place in March 2008. As part of the ESO that are still proprietary are highlighted in Deep Public Survey (DPS), imaging red and can only be downloaded by the For the first time at ESO, it is now possi­ observations were carried out in U, B, V, corresponding PI. The data request itself ble to search the archive by high-level R, I bands, using the Wide Field Imager requires authentication through the User astrophysical parameters: redshift, object (WFI) mounted at the 2.2-m telescope Portal. Note that anybody can request class, radial velocity, and wavelength. at La Silla. This survey consisted of three proprietary data, e.g. the datasets high­ In addition, dynamic consistency cross- square degrees in three well-separated lighted in red can also be requested checks of user input are performed on regions (Deep1, Deep2 and Deep3) by non PIs, but that only PIs will be able the search screen to restrict the input to split into four adjacent WFI pointings to actually download them. This mode what is actually correct for the search. (named a, b, c, d). GaBoDS combines the was made necessary to allow all users, This new interface provides users with a data from this survey with data from most irrespective whether they are PIs of ESO unified access to all advanced data prod­ other ESO programmes that coincide data or not, to freely browse the ESO uct releases and sets the path towards a with the ori­ginal DPS regions, up until archive without any prior authentication. scientific search engine. This new service December 2006. Compared to the origi­ supersedes the query form for only spec­ nal release from April 2006, there are PIs with proprietary data should note two tral advanced data products released in five more images plus associated weight important items with regard to accessing October 2007. maps. The new images include a U/38 their data via the ESO archive: image of the field Deep2c and U/50 and B/123 images in the Deep1c field. Ad- First, an archive query may return a result New data releases ditionally, V/89 and I/203 images of the for data which are not yet in the archive Deep1c field now include more data re- (thus currently unavailable for download). Several major scientific data releases sulting in increased depth. This is caused by the fact that: (a) the have taken place through the ESO information returned for queries is derived archive over the past few months and are For the latest information about the ESO from FITS header information which is summarised here. archive, or to subscribe to the archive available very soon after the data file has RSS feed, please see http://archive.eso. been created; and (b) the ingest of the Science Demonstration (SD) data from org/. For any questions or comments data into the archive can only be done the Multi-Conjugate Adaptive Optics contact us at [email protected]. after they are physically transferred to Demonstrator (MAD, see Marchetti et al., Garching. This latter process typically 2007) were released through the ESO takes 10–14 days from the time the data archive in February 2008. MAD SD runs References were obtained. If a data request is made took place in November 2007 and Janu­ Hildebrandt, H., et al. 2006, A&A, 452, 1121 for data that appear in a query result, ary 2008 and largely follow the philoso­ Marchetti, E., et al. 2007, The Messenger, 129, 8 but are not yet in the archive, those files phy applied to the Science Verification of Popesso, P., et al. 2008, A&A, submitted requested will not be available and the the VLT instruments. Tacconi-Garman, L. E. 2007, The Messenger, 130, 54

The Messenger 132 – June 2008 47 Astronomical News

FP7 E-ELT Preparation – Grant Agreement Funded by the European Commission is Underway

Roberto Gilmozzi, Guy Monnet, Figure 1. The formal exchange of the Mark Robinson (all ESO) grant agreement for the FP7 E-ELT Preparation Programme between Tim de Zeeuw, ESO Director General, and the EC Scientific Officer, Elena The aim of the FP7 E-ELT Preparation Righi-Steele. Programme is to complement the 2007– Photo: H. H. Heyer, ESO 2009 Phase B (detailed design) of the European Extremely Large Telescope (E-ELT), which is presently conducted by ESO as mandated by the ESO Council representing the 13 member states. The FP7 E-ELT Preparation Programme has a total budget of 6.013 M€, includ- ing a 5 M€ contribution from the Euro­ pean Commission under the 7th Frame­ work Programme and will run for two years, from 1 January 2008 to 31 Decem­ Key to the E-ELT endeavour is the high Science Access (WP5) will define scien­ ber 2009. The ESO executive has been level of involvement and commitment of tific requirements on key areas of the directed by Council to act as a mono- the ESO member states throughout the interaction between science users and partner in this endeavour, acting on be- life cycle of the E-ELT, making it a facility the E-ELT facility. half of all member states. The E-ELT Prep­ “for the community and by the commu­ aration Programme activities will thus nity”. This is invaluable for the establish­ Networks of Nodes of Expertise (WP6) be conducted by ESO, in collaboration ment of a comprehensive science case will help the European institutes with with 25 third-party institutes in eight and the development of crucial enabling prime expertise in the technologies cru­ member states. Figure 1 shows ESO’s technologies. It is also the vehicle by cial to the Upgrade Paths Work Package Director General, Tim de Zeeuw, and the which the complex post-focal instruments (WP9) to coordinate their work and co- EC Scientific Officer, Elena Righi-Steele, will start their respective development opt newly formed groups inside and out­ exchanging the grant agreement to mark phases. side ESO member states. the start of the project. Financial Mechanisms (WP7) will explore The aim of the E-ELT Preparation Pro­ Overall strategy and general description external public and private funding possi­ gramme Work Packages (WP) is to help bilities. ESO to be fully prepared for the antici­ The FP7 E-ELT Preparation Programme pated early 2010 decision by the funding comprises a number of transnational ac- Project Structure and Planning (WP8) is agencies in the member states to give tivities for which EC support will be inte­ focused on the preparation of the organi­ a go-ahead for building the facility. Some gral in establishing the appropriate frame­ sation of the E-ELT project structure. of the Work Packages deal with organi­ work to conduct them. Apart from “E-ELT sational matters such as: setting-up of Preparation Management” (WP1), these Upgrade Paths (WP9) will pursue, by the internal structure of the project office are: design and prototyping, the development (WP8); management of the full financial of the advanced Instrumentation and package (WP7) to build the 800 M€ plus International Cooperation (WP2) will ex- Adaptive Optics subsystems required to facility; close links with critical industries plore the possibilities of involving external further enhance the E-ELT scientific ca­- (WP3); and establishment of efficient partners for the E-ELT development and pabilities five to ten years after the start of coordination with other similar projects link it with the other planned ELT projects operations. world-wide (WP2). Optimising the science to optimise their combined scientific out­ output of the E-ELT is paramount, and put. The strategic goal of the FP7 E-ELT Prep­ further development of the Design Refer­ aration Programme is to ensure that by ence Mission (WP4) and a detailed blue­ Industrial Links (WP3) will maximise the 2010 the level of legal, financial, manage­ print for Science Access (WP5) will occur. links with industrial partners and establish rial and technical maturity required to Finally, the basic R&D knowledge for policies on connected issues, e.g. public launch the E-ELT construction is met. The ­crucial upgrades of the E-ELT observing relations and knowledge transfer. project PI is Roberto Gilmozzi, the project capabilities, e.g. for exo-planet detection, manager is Mark Robinson and his dep­ study of the first light in the Universe, etc., Design Reference Mission (WP4) will uty is Guy Monnet. The project web site will be developed (WP9) and the ESO develop a comprehensive set of observ­ is http://www.eso.org/sci/facilities/eelt/ community will organise itself in networks ing proposals and simulated science fp7-e lt /. (WP6) to be fully prepared for its future data, in particular to maintain the align­ crucial role in building powerful and inno­ ment of the E-ELT Project with its com­ The username and password can be vative focal instruments for the E-ELT munity’s scientific aspirations. ­provided on request by e-mailing facility. [email protected] or [email protected].

48 The Messenger 132 – June 2008 Astronomical News

Report on the International Workshop on Star Formation Across the Milky Way Galaxy held at ESO, Vitacura, Chile, 3–6 March 2008

Michael Sterzik, Jorge Melnick, Intended as a ‘prelude’ to the entire work- galactic discs was reviewed by Preben Claudio Melo (all ESO) shop, global star formation was intro­ Grosbøl, and the models of spiral shocks duced by Bruce Elmegreen, who outlined including clumps, magnetic fields and the main physical processes responsi- bars remain an active field of research, The workshop “Star Formation Across ble for large-scale structuring in galaxies: given the difficulties and uncertainties to the Milky Way Galaxy” brought four days gravitational instabilities; turbulent com­ precisely map the spiral structure of of intensive scientific discussions and pression; and sequential triggering. The our Galaxy on the far side (Leo Blitz). In excellent presentations to our Vitacura predictions of fundamental theoretical this context, more global agents like premises in Chile. The idea of the work­ considerations appear to agree well with the interaction with satellite galaxies, and shop was to trace star-formation activity the observed global structure of star-for­ in ­particular the LMC, may act as an spatially spanning outward from the mation regions in galaxies. external trigger for star-forming activity in Solar Neighborhood, nearby star-forming the outer parts of the Milky Way (Giovanni regions and OB associations, to spiral Starting with the immediate Solar Neigh­ Carraro). arms, the Galactic disc, around the cen­ borhood, the closest star-forming regions tral bar and bulge, and towards the allow the most detailed, and highest Is there a dominant mode of star forma­ Galactic Centre. We aimed to link differ­ ­spatial resolution studies, as reviewed by tion? According to Tom Megeath, and ent communities that usually work on João Alves. He highlighted the power of his impressive collection of images show­ specific scales and environments, and the near-infrared cloud extinction map­ ing the spatial dis­tribution of young stars thus had asked some of the most pres­ ping (NICER) technique, and discussed based on Spitzer, Chandra and ground- tigious and acknowledged scientists the relation of cloud core stability to the based surveys, there is a continuum in the field to help to develop a synoptic stellar initial mass function, and multiplic­ of scales and environments in which star view of our current understanding of ity. John Bally gave an impressive view formation happens, ranging from relative Galactic star formation. Almost all speak­ on star formation in the Orion complex, isolation to the densest regions in Giant ers in our ‘wish-list’ immediately agreed the nearest site of ongoing high- and low- Molecular Clouds (GMCs). This view is to come the long way down to Chile. This mass star formation. Orion allows to ad- backed up by the analysis of hierarchical event confirmed once again that ESO/ dress some of the most fundamental structures and substructures, and favours Chile and its faculty have become a prime questions in star formation, such as: How a scale-free fragmentation and formation address for international conferences do massive stars form? Do most stars process. of the finest scientific quality (see also the form in clusters? Are dynamical proc­ report on last year’s conference on esses dominant during star formation? In Is the stellar Initial Mass Function the “Observing Planetary Systems”, reported addition, Thierry Montmerle pointed out same in clusters and in the field? Accord­ in The Messenger, 128, 72, 2007). the relevance of the high X-ray activity of ing to Jorge Melnick, there is no evidence young stars to star and planet formation to assume the contrary (e.g., a top-heavy We present a short summary of some, through the effects of feedback. UKIDSS IMF), based on careful analysis of the subjectively selected, scientific high- and the GLIMPS survey enable deep stellar masses in several young massive lights that were discussed during views into star-formation activity in the clusters. Another, often controversial, the workshop. All 45 oral presentations Galactic Plane and were highlighted by and 19 posters contributions can be Phil Lucas. accessed and downloaded through The participants at the ESO/Vitacura conference a dedicated page: http://www.eso.org/ The classical picture of the relation of star on “Star Formation across the Milky Way Galaxy” sci/meetings/MilkyWayStarFormation/ formation and spiral density waves in assembled on the lawn.

The Messenger 132 – June 2008 49 Astronomical News

aspect of star formation in clusters is what surprisingly high star-forming effi­ ing relations, such as the relation of early mass segregation as expected from ciency and rate are found, as evidenced gas densities with star-formation rates N-body models, and Joana Ascenso either by the strong X-ray emission known from other galaxies, hold in the cautioned against an interpretation with­ ­(Sergei Nayakshin), or by the apparent Milky Way. out careful consideration of the low- over-abundance of many young O stars number statistics at the high-mass end. in the immediate surroundings of the Coffee breaks including ample snacks, Mark Gieles examined the short, but massive black hole at the centre of our well-organised poster exhibitions, and ­dramatic, phase when expulsion of natal Galaxy (Andrea Stolte), which seems to delicious cocktails in the garden of our gas from clusters results in “infant mortal­ bias the IMF in this environment. Vitacura office contributed to the friendly ity”. Hans Zinnecker reminded us that and stimulating atmosphere of this probably up to half of all stars in the Milky Francesco Palla concluded and summa­ ­workshop. The conference dinner in the Way form in open clusters. rised the workshop with an excellent vineyard Casa del Bosque will remain ‘postlude’. With our current understand­ a ­memorable event for many participants. Stellar populations towards the inner ing, the ‘problem’ of star formation is Many thanks to Maria-Eugenia Gomez bulge and bar were reviewed by Fred probably not solved. There is a bewilder­ and her team who, once again, managed Schuller (as seen through ISO, Spitzer, ing diversity of star-forming regions, and flawless and efficient local organisation and APEX), and Livia Origlia (through a continuum of star formation from isola­ for more than 100 guests. We are all look­ characterisation by their kinematical, tion to dense clustering, on many scales, ing forward to next year’s ESO workshop chemical and evolutionary properties, and no single theory may be able to hosted in our ESO-Chile ‘science head­ mainly from near-infrared spectroscopy). catch and explain all relevant processes. quarters’! Towards the Galactic Centre a some- It remains also to be seen if global scal-

Announcement of the ESO Workshop on Large Programmes

13–15 October 2008, Garching, Germany

Over the first ten years of science opera­ The presentations will be followed by a tions of the VLT, 15 % of the science time discussion session on the general scien­ has been devoted to the execution of tific impact of ESO facilities. Large Programmes. In May 2003, ESO organised a Large Programmes work­ One of the outcomes of the May 2003 shop to obtain a first assessment of the Large Programme workshop was a sug­ Photo: H. H. Heyer, ESO scientific return of Large Programmes. gestion that ESO store the legacy data In agreement with its Observing Pro­ products of Large Programmes in its sci­ grammes Committee (OPC), ESO is plan­ ence archive. This suggestion was imple­ ning a further overview of the scien- mented with the requirement that Large tific results achieved through Large Programmes that started after 1 April Programmes conducted at the La Silla 2005 deliver Advanced Data Products Paranal Observatory. To this effect, (ADP) to the ESO archive at the time ESO is organising a three-day workshop of publication of their results in a refereed in Garching. journal. The workshop will also feature a presentation of the ADP submission The workshop will feature scientific pres­ process and a discussion of its value to entations of all Large Programmes the ESO scientific community. that have been completed since the May 2003 workshop. The teams of inves­ For further details of the workshop, tigators in charge of these Large Pro­ please refer to http://www.eso.org/sci/ grammes will be invited to present their meetings/LP2008/, where the registra- scientific results, and the impact that tion form can also be found. The registra­ their project has had on its particular field. tion deadline is 15 July 2008.

50 The Messenger 132 – June 2008 Astronomical News

Announcement of the Topical Symposium “Science with the E-ELT” at JENAM 2008

8–12 September 2008, Vienna, Austria

The next Joint European Astronomy observing facility for European Astron­ Input from the community is eagerly Meeting and National Astronomy Meeting omy, the European Extremely Large Tele­ sought on every aspect of such a facility: (JENAM) will be held on 8–12 September scope (E-ELT) project, which is now in scientific impact, including in synergy 2008 in Vienna (Austria). Its unifying the midst of its three-year (2007–2009) with other major observatories on ground theme is to explore the “New Challenges detailed design study and due for deci­ and in space; technical and operation- to European Astronomy”. In that frame­ sion to build by early 2010. Prime motiva­ al requirements to get maximum science work, ESO and Opticon are jointly organ­ tions are to inform the community on the value. To participate to the Symposium, ising one of the nine JENAM 2008 top­ical scientific perspectives opened up by you just need to register for the main Symposia, viz. Symposium #1 on “Sci­ such a facility and, especially, to gather JENAM event at http://www.univie.ac.at/ ence with the E-ELT”. feedback on the science goals and re- jenam2008/. Your contribution to the quirements needed to help make the debate will be invaluable to help steer the This Symposium is a timely opportunity E-ELT the best possible scientific tool for project to the future needs of European to discuss and assess the main science European astronomy in the next decades. astronomers. goals of a major potential ground-based

Fellows at ESO

months. I very much like the practical side and taking a year out, I started a PhD of the job, i.e. being involved in the oper­ at the Royal Observatory in Edinburgh ations of the observatory, and eventually investigating X-ray detected AGN in gal­ transferred to complete my fellowship axy clusters. in Chile. My scientific research interests have expanded, primarily through new Although I mainly worked with X-ray data collaborations at ESO, and now include for my research, the highlights of my PhD studying massive galaxies at high red­ were the occasional trips to ‘real’ ob- shift, clusters of galaxies at high redshift servatories in Chile and La Palma. After and using planetary nebulae as dynami­ surviving, and enjoying, the exhaust- cal tracers in nearby clusters of galaxies. ing experience of a five-night run on the INT in January, I was keen to work at Michelle Doherty an observatory. This fitted well with my scientific aims of obtaining optical data My interest in Astronomy began in the for my X-ray sources, as well as my final years of high school and continued desire to work in a different culture, so I throughout my undergraduate studies accepted an ESO fellowship in 2005. in physics at the University of Sydney. I wrote my final Honours thesis in astron­ I have found the experience of working at omy and subsequently moved to England Paranal both challenging and enjoyable. to pursue a PhD at the Institute of Astron­ Being part of a large team, with problems omy, Cambridge. There I worked with the to be solved in real time, is quite different instrument CIRPASS (Cambridge Infra­ from my research life back in Santiago. It Red Panoramic Survey Spectrograph), has been interesting to learn about so developing an interest in near-infrared many different observing techniques, and spectroscopy and, in particular, fibre-fed Rachel Gilmour the buzz of the observatory means that spectroscopy. there is always something new going on. I Unlike many astronomers, as a teenager I particularly enjoy the opportunities to During my doctorate I worked on pro- was not at all interested in astronomy, meet scientists with many different speci­ jects related to the star-formation rates of particularly the practical sort that involved alities, and to observe the whole spec­ distant galaxies (at redshift z ~ 1) and the standing in the cold drizzle waiting for a trum of (optical) astronomical objects, nature of extremely red galaxies at high gap in the clouds! However, whilst study­ from planets to gamma-ray bursts. I plan redshift. After receiving my PhD in 2005 ing physics at university I found myself to expand on these interests in the forth I moved to ESO Garching to take up a in the astronomy building at midnight on year of my fellowship, when I hope to go ­fellowship. For my duties I chose to be a Friday, and realised that I was hooked. to a UK institute to continue my research involved in science operations at Paranal, After completing my Masters project and to learn more about communicating travelling out to Chile once every three at Oxford looking for gravitational lenses, astronomy with the public.

The Messenger 132 – June 2008 51 Astronomical News

ESO

European Organisation for Astronomical Research in the Southern Hemisphere

ESO Fellowship Programme 2008/2009

The European Organisation for Astronomical Research in the South­ Planck Institutes for Astrophysics and for Extraterrestrial Physics ern Hemisphere awards several postdoctoral fellowships each and only a few kilometres away from the Observatory of the Ludwig- year. The goal of these fellowships is to offer outstanding young sci­ Maximilian University. ESO is participating in the newly formed entists the opportunities and facilities to enhance their research Excellence Cluster on astrophysics on the Garching Campus. In ­programmes by promoting close contact between young astrono­ Chile, fellows have the opportunity to collaborate with the rapidly mers and the activities and staff at one of the world’s foremost expanding Chilean astronomical community in a growing partner­ observatories. ship.

With ALMA becoming operational in a few years, ESO offers ALMA We offer an attractive remuneration package including a competi- fellowships to complement its regular fellowship programme. tive salary (tax-free), comprehensive social benefits, and provide ­Applications by young astronomers with expertise in mm/sub-mm financial support for relocating families. Furthermore, an expatriation astronomy are encouraged. allowance as well as some other allowances may be added. The outline of the terms of service for fellows (http://www.eso.org/public/ In Garching, the fellowships start with an initial contract of one year employment/fellows.html) provides some more details on employ­ followed by a two-year extension (three years total). The fellows ment conditions/benefits. spend up to 25 % of their time on support or development activities in the area of instrumentation, operations support, archive/virtual Candidates will be notified of the results of the selection process observatory, VLTI, ALMA, ELT, public affairs or science operations at between December 2008 and February 2009. Fellowships begin the Observatory in Chile. between April and October of the year in which they are awarded. Selected fellows can join ESO only after having completed their In Chile, the fellowships are granted for one year initially with an ­doctorate. extension of three additional years (four years total). During the first three years, the fellows are assigned to one of the operation groups The closing date for applications is 15 October 2008. on Paranal, La Silla or APEX/ALMA. Fellows contribute to the opera­ tions at a level of 80 nights per year at the Observatory and 35 days Please apply by filling the web form available at the recruitment page per year at the Santiago Office. During the fourth year there is no http://jobs.eso.org attaching to your application (preferred format is functional work and several options are provided. The fellow may be PDF): hosted by a Chilean institution (and will thus have access to all tele­ – your Curriculum Vitae including a list of (refereed) publications scopes in Chile via the Chilean observing time). Alternatively, she/he – your proposed research plan (maximum two pages) may choose to spend the fourth year either at ESO’s Astronomy – a brief outline of your technical/observational experience Centre in Santiago, or at the ESO Headquarters in Garching, or (maximum one page) at any institute of astronomy/astrophysics in an ESO member state. In addition three letters of reference from persons familiar with your In addition to pursuing independent research, all fellows have scientific work should be sent directly to ESO to [email protected] ample opportunities for scientific collaboration within ESO, both in by the application deadline. ­Garching and Santiago. For more information about ESO’s astro­ nomical research activities and available projects open for collabo­ Please also read our list of FAQs at http://www.eso.org/sci/activities/ rations to fellows please consult http://www.eso.org/sci/activities/ ESOfellowship-faq.html regarding fellowship applications. ESOfellowship.html. A list of current ESO staff and fellows and their research interests can be found at http://www.eso.org/sci/activities/ Questions not answered by the above FAQ page can be sent to: personnel.html. Additionally, the ESO Headquarters in Munich, Marina Rejkuba, Tel +498932006-453, Fax +498932006-4 80, ­Germany, is situated in the immediate neighbourhood of the Max- e-mail: [email protected]

52 The Messenger 132 – June 2008 Astronomical News

New Staff at ESO

ing this talented, friendly group so close education of students and faculty boards, to the beginning of commissioning obser­ I now enjoy being closer to instrumen­ vations, which will take place towards tation and observational issues. For me the end of the year. Taming the many and there is a very fruitful interplay between subtle aspects of this facility will be a excellent science and expert knowledge demanding task, but I expect it to be of instruments. Most of my research pro- rewarding in equal measure as we use its jects focus on galaxy formation and evo­ unprecedented angular resolution to lution within a cosmological context. The catch unmatched glimpses of nearby projects provide strong constraints for worlds. models like the cold dark matter (CDM) based hierarchical build-up of cosmic The additional challenge of leaving the structure by measuring the mass evolu­ US West Coast and moving my whole tion, star-formation history and chemical family to lovely Bavaria has presented enrichment of galaxies. The observa- some unique hurdles, but we are thrilled tions are mainly achieved with optical to have the opportunity to enjoy life in spectroscopy, using ESO’s very efficient Munich and the surrounding areas in a instruments, of distant galaxies out to Gerard Van Belle way that is much more intimate than a redshift unity, combined with deep opti­ tourist sees. Such a big move is always cal/NIR photometry and spatially highly- I joined ESO in September 2007 as the bound to have its painful moments, but resolved Hubble Space Telescope imag­ PRIMA Instrument Scientist for the VLTI. we have found no shortage of new ing. For the interpretation of the results Over the years I have had the distinct friends at ESO and in our new neighbour­ we compare the observational data with pleasure to work with a variety of excel­ hood that have helped smooth the transi­ N-body/Smoothed Particle Hydrodynam­ lent teams on a number of optical inter­ tion. My family and I thank alll those in ics (SPH) simulations of galaxy evolu- ferometry projects, and it seemed a natu­ Garching and Neufahrn who have been tion considering various interaction phe­ ral step forward to accept an offer to so hospitable to us. nomena. Targeting not only field galax- join the PRIMA group in Garching. Previ­ ies but also groups and clusters, we ously I had worked on the Keck Interfer­ explore the environmental dependence of ometer as an instrument architect, and Bodo Ziegler galaxy evolution. observed extensively with the Palomar Testbed Interferometer, the CHARA Array Since last December I have been enjoy­ Now in the lively community of ESO, I’m and the IOTA Array, so joining ESO in this ing the scientific environment, the in- looking forward to many fruitful discus­ capacity is a welcome new challenge. strumental expertise and the cooperative sions of both scientific and observatory- spirit of colleagues at ESO as a new related issues. PRIMA to me represents the final, full member of the User Support Depart­ flowering of the first generation of VLTI ment. I support programmes conducting instruments, and has a real opportunity observations with the FORS1 and FORS2 to showcase the truly unique capabilities spectrographs in all modes (IMG, HIT, – and discoveries – possible only with LSS, MOS, PMOS, MXU) and with the re- interferometry. The PRIMA team mem­ cently commissioned HAWK-I near-infra­ bers, both inside and outside ESO, have red camera. Being the link between users been working hard on the project for from the general astronomical community Photo: H. H. Heyer, ESO many years, and I feel a little spoiled join­ and ESO Paranal staff, I try to maximise the scientific return of observing runs for the given instrumental and technical fea­ sibility. Other tasks are related to the ESO survey team that is responsible for an efficient implementation and execution of the public large-scale surveys to be con­ ducted at the new survey telescopes VST and VISTA.

Before joining ESO I was the head of a Junior Research Group supported by the Volkswagen Foundation at the Univer­ sity of Göttingen for almost seven years and temporary professor at the University of Bonn for half a year. Having spent much of my time on administrative issues,

The Messenger 132 – June 2008 53 Astronomical News

Exploring the Cold Universe – A Planetarium Show for the IYA 2009

Henri Boffin1 with a total annual visitorship of about deavour that the ALMA project repre­ Agnès Acker 2, 3 1.3 million. As member of the Internation- sents. The unique setting of ALMA in the al Planetarium Society, the APLF has also Atacama Desert at an altitude of 5 000 m established close links with planetaria is also emphasised, as well as the diffi­ 1 ESO from many other countries. culty of building something in such a re- 2 Observatoire de Strasbourg, France mote, inhospitable place. An astronomer 3 Association des Planétariums In 2001, the APLF, in collaboration with will act as the primary guide through the de Langue Française (APLF) the French space agency CNES, pro­ show. The aim is to have a spectacle that duced a show about the Earth seen from is attractive to all members of the public, space. In 2002, in collaboration with ESO, from young to old. A planetarium show highlighting the a very successful show was produced ALMA project is being jointly prepared for the 40th anniversary of ESO, entitled ESO provides the scientific expertise, val­ by ESO and the Association des Plané- “Mysteries of the Southern Sky”, cele­ idates the story-board, supplies images, tariums de Langue Française. brating the performance of the VLT. In computer simulations and videos, and both cases, the shows were presented in financially supports the project. ESO will around 40 planetaria in France, Germany, also produce a Chilean version and help As part of a wide range of education and Belgium, Italy, and Spain and other coun­ provide associated documents for visi­ public outreach activities for the Interna­ tries. tors. The APLF will make the story-board, tional Year of Astronomy 2009 (IYA 2009), produce the show in five languages, and ESO is collaborating with the Association About 30 planetaria in several countries is responsible for the promotion, duplica­ des Planétariums de Langue Française have already agreed to present the tion and distribution both in France and in (APLF, the association of French-speak­ new show which will be available for Europe. ing planetaria) and other partners in Eu- viewing from autumn 2008 – in order to rope to produce a new 30-minute long be included in school programmes – The show shall be available in three dif­ planetarium show centred on the ALMA and officially inaugurated early in 2009. ferent formats: full dome video; All-Sky project. It is a unique chance for planetaria to projection and video windows; image be directly involved with the IYA 2009. projection and video windows for smaller This show builds on the experience planetaria. It will be available to all plan- already gained by the APLF to produce etaria worldwide for a very small fee, de- unique planetarium shows at the Euro­ A fruitful collaboration pendent on the type of planetarium, to pean level. The APFL, born in 1984 but cover basic costs. officially created in 1989, coordinates the The emphasis of the new planetarium operations of about 50 French planetaria show is the incomparable scientific en-

Left: A photograph of the Chajnantor plateau with superposed 3D computer rendering of some ALMA antennas as they might appear when ALMA is opera­ tional. Photo: H. H. Heyer, 3D Computer Rendering: L. Calçada and H. Zodet (all ESO)

Right: A view towards the VLT and the summit of Cerro Paranal with the VISTA dome in the foreground.

54 The Messenger 132 – June 2008 Astronomical News

Personnel Movements

Arrivals (1 April–30 June 2008) Departures (1 April–30 June 2008) Europe Europe Biggs, Andrew (GB) Astronomer Dolensky, Markus (A) Software Engineer Brucker, Cordula (D) Secretary/Assistant Kotzlowski, Heinz E. (D) Mechanical Engineer Checcucci, Alessio (I) Software Engineer Madrid Pariente, Silvia (E) Secretary/Assistant Forchi, Vincenzo (I) Software Engineer Muradore, Riccardo (I) System Engineer Galametz, Audrey (F) Student Pedicelli, Silvia (I) Student Heymann, Frank (D) Student Teimoorinia, Hossein (IR) Student Jalali, Behrang (IR) Student Wallander, Anders (S) Software Engineer Kern, Lothar (D) Electrical/Electronics Engineer Larsen, Jonas (DK) Software Engineer Lilley, Paul (GB) Electronic Engineer Rose, Elke (D) Secretary Yagoubov, Pavel (NL) System Engineer Chile Chile Ahumada, Andrea Veronica (RA) Fellow Duran, Domingo (RCH) Electrical Assistant Bourget, Pierre (F) Instrumentation Engineer Gardiazabal, Jose (RCH) Software Engineer Caceres, Francisco (RCH) Telescope Instruments Operator Herrera, Leonardo (RCH) Electronic Engineer de Graauw, Mattheus Thijs (NL) ALMA Director (Interim) Jimenez, Jorge (RCH) Instrument Technician Gallegos, Leonardo (RCH) Telescope Instruments Operator Reveret, Vincent (F) Operations Astronomer Kuo, Caterina (RCH) Procurement Clerk Robinson, William (RCH) Mechanical Engineer Ma, Qiao Yun (RCH) Accountant Salinas, Alejandro (RCH) Network Specialist Merand, Antoine (F) Operations Astronomer Vanzi, Leonardo (I) Operations Astronomer O’Neal, Jared (USA) Instrumentation Engineer Reinero, Claudio (RCH) Software Engineer Rivas, Leonel (RCH) Telescope Instruments Operator Romero, Cristian (RCH) Telescope Instruments Operator Slusarenko, Nicolas (RCH) Software Engineer Photo: H. H. Heyer, ESO

The Messenger 132 – June 2008 55 ESO is the European Organisation for Contents Astronomical Research in the Southern Hemisphere. Whilst the Headquarters The Organisation (comprising the scientific, technical and T. de Zeeuw – The Perfect Machine 2 administrative centre of the organisa- 10th Anniversary of First Light of the VLT 4 tion) are located in Garching near Austria Declares Intent to Join ESO 5 ­Munich, Germany, ESO operates three observational sites in the Chilean Ata­- Telescopes and Instrumentation cama desert. The Very Large Telescope M. Kissler-Patig et al. – Hawk-I – First Results from Science Verification 7 (VLT), is located on Paranal, a 2 600 m M. Sarazin et al. – Seeing is Believing: New Facts about the Evolution of high mountain south of Antofagasta. At Seeing on Paranal 11 La Silla, 600 km north of Santiago de C. Snodgrass et al. – EFOSC2 Episode IV: A New Hope 18 Chile at 2 400 m altitude, ESO operates I. Saviane, L. Monaco – Two Volume-phased Holographic Grisms several medium-sized optical tele­ Now Available for EFOSC2 20 scopes. The third site is the 5 000 m M. Kraus et al. – The ALMA Antenna Transporter 23 high Llano de Chajnantor, near San R. Laing – Recent Progress at the ALMA Test Facility 28 Pedro de Atacama. Here a new submilli- H. Vázquez Ramió et al. – Cute-SCIDAR at Paranal for metre telescope (APEX) is in opera- E-ELT Site Characterisation 29 tion, and a giant array of 12-m submil- limetre antennas (ALMA) is under Astronomical Science development. Over 2 000 proposals are D. Reimers et al. – The Antares Emission Nebula and Mass Loss of a Sco A 33 made each year for the use of the ESO M. Matsuura et al. – SINFONI Observations of Comet-shaped Knots telescopes. in the Planetary Nebula NGC 7293 (the Helix Nebula) 37 M. G. Haehnelt et al. – Hunting for the Building Blocks of Galaxies The ESO Messenger is published four like our own Milky Way with FORS 41 times a year: normally in March, June, September and December. ESO also Astronomical News publishes Conference Proceedings and N. Delmotte – News from the ESO Science Archive Facility 47 other material connected to its activi- R. Gilmozzi, G. Monnet, M. Robinson – FP7 E-ELT Preparation – ties. Press Releases inform the media Grant Agreement Funded by the European Commission is Underway 48 about particular events. For further M. Sterzik, J. Melnick, C. Melo – Report on the International Workshop in­formation, contact the ESO Public on Star Formation Across the Milky Way Galaxy 49 ­Affairs Department at the following ad- Announcement of the ESO Workshop on Large Programmes 50 dress: Announcement of the Topical Symposium “Science with the E-ELT” at JENAM 2008 51 ESO Headquarters Fellows at ESO – M. Doherty, R. Gilmour 51 Karl-Schwarzschild-Straße 2 ESO Fellowship Programme 2008/2009 52 85748 Garching bei München New Staff at ESO – G. Van Belle, B. Ziegler 53 Germany H. Boffin, A. Acker – Exploring the Cold Universe – A Planetarium Show Phone +498932006-0 for the IYA 2009 54 Fax +49893202362 Personnel Movements 55 [email protected] www.eso.org

The ESO Messenger: Editor: Jeremy R. Walsh Technical editor: Jutta Boxheimer Technical assistant: Mafalda Martins www.eso.org/messenger/

Printed by Peschke Druck Schatzbogen 35 81805 München Front Cover Picture: Ten years since Germany VLT First Light: a view of Paranal and the Galactic Plane before sunrise. © ESO 2008 Photograph by Hans Hermann Heyer ISSN 0722-6691 (ESO).