The Messenger

No. 172 – June 2018 Enhanced data discovery services for the ESO Science Archive Science services ESO the discovery data for Enhanced GRAAL using optics adaptive of HAWK-I Verification Science stars starburstin galaxies massive many too finds ALMA ALMA and VLTI with surface imaging Stellar

The Messenger 172 – June 2018 1 Telescopes and Instrumentation DOI: 10.18727/0722-6691/5073

Enhanced Data Discovery Services for the ESO Science Archive

Martino Romaniello 1 and the Atacama Pathfinder Experiment the characteristics and limitations of Stefano Zampieri 1 (APEX) antenna at Chajnantor. Also each collection of processed data. This Nausicaa Delmotte 1 ­available through the archive are data is particularly­ important, as it enables Vincenzo Forchì 1 from selected non-ESO instruments at users to decide whether the data are Olivier Hainaut 1 La Silla, for example, the Gamma-Ray suitable for their specific science goals. Alberto Micol 1 burst Optical/Near-infrared Detector The systematic archive publication of such Jörg Retzlaff 1 (GROND), the Fibre-fed Extended Range processed data dates back to 25 July Ignacio Vera 1 Echelle Spectrograph (FEROS) and the 2011, with the first products produced by Nathalie Fourniol 1 Wide Field Imager (WFI). It also includes the Public Surveys conducted with the Mubashir Ahmed Khan 1 raw data for UKIDSS, the infrared deep Visible and Infrared Survey Telescope Uwe Lange 1 sky survey using the wide-field camera for Astronomy (VISTA) infrared camera Devendra Sisodia 2 WFCAM at the United Kingdom Infrared VIRCAM (Arnaboldi & Retzlaff, 2011). Malgorzata Stellert 3 Telescope (UKIRT) in Hawaii. In addition, ­Processed data that were generated at Felix Stoehr 1 ESO hosts and operates the European ESO have been available since September Magda Arnaboldi 1 copy of the ALMA Science Archive 2013. An up-to-date overview of the Chiara Spiniello 1, 4 (Stoehr et al., 2017). The integration of released data is available online for con- Laura Mascetti 5 archive services for LPO and ALMA data tributed and pipeline processed data 2, 3. Michael Fritz Sterzik 1 is discussed here. The number of users accessing pro- Over the years, the archive has steadily cessed data in the archive has grown 1 ESO grown into a powerful scientific resource steadily over time (Figure 1). At the cur- 2 Pactum Limited, London, UK for the ESO astronomical community. rent rate, an average of 2.2 new users 3 TEKOM Industrielle Systemtechnik As processed data are routinely included, are added every working day, with each GmbH, Gautin, Germany they can be used directly for scientific user placing 11 requests on average. 4 INAF–Osservatorio Astronomico di measurements, thus alleviating the need Given the growing popularity within the Capodimonte, Naples, Italy for users to carry out data processing community, and the increasing volume 5 Terma GmbH, Darmstadt, Germany on their own. An in-depth analysis of the and complexity of the archive holdings — archive usage and user community is and taking into account the recommen- presented in Romaniello et al. (2016). dations of advisory bodies, such as the The archive of the La Silla Paranal Users Committee, the Public Survey Observatory is a powerful scientific The archive is populated with processed Panel, and the results of the community resource for the ESO astronomical data through two channels. For the first working group report on science data community. It stores both the raw data channel, data-processing pipelines are management (STC Report 580 4) — it has generated by all ESO instruments and run at ESO for selected instrument modes become necessary to upgrade the ways selected processed data. We present to generate products that are free from in which users can access the ESO new capabilities and user services that instrumental and atmospheric signatures ­Science Archive in order to enhance data have recently been developed in order and that have been calibrated. They discovery and usage. to enhance data discovery and usage cover virtually the entire data history of in the face of the increasing volume the corresponding instrument modes and The trajectory of contemporary astro- and complexity of the archive holdings. are generated by automatic processing, nomical research increasingly involves Future plans to extend the new services with no knowledge of the associated multi-epoch, multi-messenger, multi- to processed data from the Atacama ­science case. Checks are in place to wavelength, multi-facility science, in Large Millimeter/submillimeter Array identify quality issues with the products. which data are plentiful and varied. At (ALMA) are also discussed. The second­ channel involves data prod- the same time, data acquired from ucts that have been contributed by the ­different facilities are becoming ever community, which have been generated more complex, yet have to be combined Background and motivation with processing schemes optimised to in order to tackle increasingly challenging serve specific science cases. In most scientific questions. In this context, the The ESO Science Archive 1 began oper­ cases, they have already been used to role of science data archives is to lower ating in its current form in 1998, a few derive published results (see Arnaboldi the access threshold that separates months ahead of the start of science et al., 2014). These contributed datasets, researchers from acquiring and being operations of the Very Large Telescope, which are validated via a joint effort able to work with the data that they are the VLT (see Pirenne et al., 1998). It is between the providers and ESO before interested in. The average astronomer the operational, technical and science ingestion into the archive, often include cannot be expected to be intimately data archive of the La Silla Paranal advanced products like mosaiced familiar with the details of each archive Observatory (LPO). As such, it stores all images, source catalogues and spectra. and, even less, with the details of the of the raw data, including the ambient instruments that produced the datasets weather conditions, from the LPO, i.e., Thorough user documentation is also concerned. The access layer to the data the telescopes at Paranal and La Silla, provided for all data releases, detailing therefore has to be as self-­explanatory as

2 The Messenger 172 – June 2018 2800 Figure 1. The growth include expanding the support to ALMA Distinct users of of distinct users of processed data and raw data from the archive processed data ­processed data in the archive as a function LPO. It is planned that these new access of time. The green line points will gradually replace the current 2100 displays access to prod- ones for La Silla Paranal data, while ucts contributed by the ALMA will keep maintaining a dedicated, community (deployed s on 25 July 2011), the separate access.

user 1400 blue line shows access . to products generated No at ESO (deployed on The ESO Archive Science Portal 10 September 2013), and the orange line is 700 for access to either type The most immediate way to access the of products. new archive services is through a web application, the ESO Archive Science — Generated at ESO 7 0 — Contributed by the Portal , using any recent version of the 14 29 13 29 14 28 16 community most popular internet browsers. A 7- 0- 2- 1- 3- -06- -0 -09- -1 -1 -0 -0 — Either one screenshot of its landing page is shown 11 12 13 14 15 17 18 20 20 20 20 20 20 20 in Figure 2. The window is divided into Time three main sections: a sky view in which the content of the ESO archive is dis- possible so as to present the data in a ­discoverable and handled so that they played together with background imagery user-friendly way, rather than couched can be used together with datasets from such as the DSS; a table in which details in the technical terms used within the other observatories and data centres. of individual datasets are shown and from archive itself (for example, as calibrated The natural framework for this is within which further actions can be triggered, fluxes and wavelengths, rather than the Virtual Observatory (VO); compatibility such as accessing previews; and a section detector counts, or an engineering and interoperability with the VO is there- in which query constraints can be speci- description of the instrument setup). fore a high-level goal for this project. fied, by explicitly entering them and/or by selecting values or ranges of values In this first release, processed data from arranged in facets. Query results can be Access points to the data the LPO are supported. Future plans sent to suitable external applications for

Different types of user interaction are Figure 2. The landing web page of the ESO Archive coordinate or name, as resolved by the CDS’s supported: Science Portal. The celestial sphere is colour-coded ­Sesame service 8. In order to serve different use – Interactive access: web pages through according to the types of ESO data contained at cases, they are a combination of physical charac­ each position (the sky viewer is CDS’ AladinLite6, the teristics of the data (e.g., signal-to-noise ratio, which users can browse and explore web version of Aladin). The entire content of ­sen­sitivity, spectral range covered, spectral reso­ the assets with interactive, iterative the archive is presented through aggregations of lution), the observational setup (e.g. filter name, queries. The results of such queries 17 parameters, which can also be used to enter exposure time) and the ESO observing process are presented in real time in various query constraints, in addition to querying by object (e.g. PI name, Programme ID). tabular and/or graphic forms, allowing an evaluation of the usefulness of the data which can then be selected for retrieval. – Programmatic access: whereby users are able to formulate complex queries through their own programmes and scripts, obtain the list of matching assets, and retrieve them. – Access by tools: whereby data are ­discovered, selected and accessed through tools normally developed by third parties, which are external to the web access channel. These tools often implement sophisticated data handling capabilities, such as TOPCAT 5 for catalogues, or Aladin 6 for images.

Furthermore, in order to fulfil the potential of multi-wavelength, multi-messenger science, ESO data need to be easily

The Messenger 172 – June 2018 3 Telescopes and Instrumentation Romaniello M. et al., Enhanced Data Discovery Services for the ESO Science Archive

further specialised analysis. To this end, the ESO Archive Science Portal commu–­ nicates via the SAMP 9 protocol, which is supported by popular astronomical tools like TOPCAT and Aladin, enabling them to receive information easily.

Multi-dimensional faceted search In order to serve a broad range of use cases, 18 query parameters are openly available. They are a combination of posi- tional parameters (cone search around a given position on the sky), physical characteristics of the data (for example, signal-to-noise ratio, sensitivity, spectral range, spectral and spatial resolution), the observational setup (for example, filter name and exposure time), and the ESO observing process (for example, Principal Investigator [PI] name and Programme ID). Since many parameters are intrinsically interdependent, constraining one param- eter typically restricts the meaningful range of one or more of the others. As a simple example, specifying a PI restricts the choices of Programme IDs to their any previous knowledge. For example, Figure 3. The all-sky search and rendering capabili- programmes. as shown in Figure 3, it is immediately ties of the ESO Archive Science Portal make it easy to find and visualise data collections that span large apparent that the archive contains data areas of the sky. In the example above, the footprint In order to cope with this, the query of several ­different types, including spec- of the VVV Public Survey covering 630 square parameters and search results are trum, catalogue, image, image cube degrees is shown on the all-sky DSS imagery. The grouped according to facets, so the user and visibility (the counts for each of these level of transparency reflects the relative number of VVV images in the different locations on the sky. can easily be exposed to and navigate categories are also provided). The equiva- the multidimensional space of the archive. lent information and grouping are available Wikipedia defines facets as follows 10: for all other search parameters. information. In terms of spatial­ extent, “A faceted classification system classifies the ESO archive contains datasets that each information element along multiple With this approach, searches flexibly range from individual pointings to covering explicit dimensions, called facets, ena- adapt to input from the users, guiding significant fractions of the celestial sphere bling the classifications to be accessed them through the content of the archive, — the whole hemisphere in the case of and ordered in multiple ways rather than rather than limiting them to a pre-defined the VISTA Hemisphere Survey (VHS) in a single, pre-determined, taxonomic set of possible paths. ­public survey. This large spatial dynamic order”. This concept may be familiar from range is handled by adopting the Hierar- most e-commerce sites. In practice, at Previews, hierarchical views and chical Equal Area isoLatitude Pixelation any given time the user is presented with footprints (HEALpix) pixellation 11 of the celestial the available parameter space accounting A preview is a lightweight, faithful repres­ sphere (see Figure 3). for the previously specified constraints. entation of the actual data, which allows In our simple example of specifying a PI the user to evaluate their usefulness Customised previews are offered for name, the choices in the facet of the ­without transferring the full-size file(s). ­different data types, which include the ­programme ID will be limited to the pro- They are needed for a swift but in-depth possibility of user interaction (for example, grammes by that PI. assessment of the data, beyond the zooming and panning) to navigate through characterisation provided by the faceted the different spatial and spectral scales Two additional features are offered to query parameters described above. within the data. An example of a preview ease navigation. Where appropriate, of a spectrum is shown in Figure 4.­ Image entering the constraints is supported Data exposed through the ESO Archive previews are rendered with a hierarchical by auto-completion. Also, the possible Science Portal display a great variety. For tiling mechanism called Hierarchical values that a query parameter can take example, the range in images spans a few ­Progressive Surveys (HiPS) 12, which adap- are grouped and presented as histograms million to several hundred million pixels; in tively provides the appropriate spatial or lists, as appropriate. In this way, the spectra it covers a few hundred to several scale at any given zoom level, resulting in system communicates its content to hundred thousand spectral channels; a responsive and satisfactory user experi- users at all times, without the need for and data cubes provide simultaneous 3D ence. An example is shown in Figure 5, in

4 The Messenger 172 – June 2018 Wavelength: 384.600 Figure 4. Example of a spectrum preview: the star Flux: 1.610e–11 Hip058859 as observed with the X-shooter instru- SNR: 548.416 ment. Dynamic interactions are possible in order to 7.5e–11 evaluate the quality of the data and determine that they are fit for the intended purpose, e.g., by interac- tively zooming in on a spectral region of ­interest (inset). 5e–11 –1 Å

–1 2.5e–11 which the preview of a tile from the VISTA s

–2 Variables in The Via ­Lactea (VVV) Public

cm 0 Survey is superimposed on an image from g the Digitized Sky Survey (DSS). On-sky er –2.5e–11 footprints can be superimposed on an image of the celestial sphere to place the –5e–11 data in context and assist in browsing and 300325 350375 400425 450475 500525 550 1000 selection (see Figure 6 for an example).

500 R

SN 0 Direct database and Virtual Observatory access –500 300325 350375 400425 450475 500525 550 The inherent limitation in the intuitive way that the web interface enables archive content to be discovered is that it is unsuited to more complex queries, such 300 325350 375400 425450 475500 525550 as those that include sequences with ­logical statements like “and”, “or” and

1.4e–11 “not”, or queries that join different sources of information. This restriction can be 1.2e–11 –1

Å overcome by bypassing the web interface,

–1 1e–11 s thus providing direct access to the ESO –2 13 cm 8e–11 database tables . By adhering to widely g er 6e–11 recognised standards developed by the International Virtual Observatory Alliance 4e–11 14 470475 480485 490495 500505 510 (IVOA) , the ESO data can be queried alongside data from other observatories and data centres. This brings the ESO data into the appropriate general context of multi-wavelength, multi-messenger science.

Programmatic access Users can specify their own custom ­queries via a standard service protocol using the IVOA’s Astronomical Data Query Language, ADQL15. The service

Figure 5. A preview of one tile from the VVV Public survey is shown superimposed on the backdrop of the DSS. The ­preview itself was generated using the HiPS mechanism and can be interacted with by zooming and panning on it. A full-resolution zoom on the inner-most regions of the ­stellar cluster in the tile is shown in the inset. Zooming in dynamically loads the appropriate spatial hierarchy, which provides for a respon- sive and ­satisfactory user experience.

The Messenger 172 – June 2018 5 Telescopes and Instrumentation Romaniello M. et al., Enhanced Data Discovery Services for the ESO Science Archive

templates for users to customise and adapt to their specific needs 26.

A VO data link service 27 has also been implemented. It provides access to scien- tific data, their ancillary files (for example, weight maps), previews and data docu- mentation. It also lists information related to provenance (such as the data files that were used to derive these products, and any data that were produced using these files). The VO Simple Spectral Access (SSA) service 2 8 provides easy browsing and access capabilities for the 1D spec- troscopic data.

Tool access

The same basic infrastructure behind programmatic access allows users to browse the ESO archive from VO-aware applications. This enables users to ­discover and access ESO data through stand-alone tools, which have powerful generic and/or specific capabilities that cannot be implemented in a general interface. Examples of such external tools include TOPCAT and Aladin, as well as tools like SPLAT-VO and other clients that implement the Simple Spectral Access Figure 6. Examples of footprints of imaging data sophisticated “point in footprint” query Protocol (SSAP) of the VO. To achieve towards the Galactic Centre: VIRCAM data from the (for example, if a user wishes to find this, all ESO VO-compliant data services VVV Public Survey, OmegaCAM data from the VST Photometric Hα Survey of the Southern Galactic the progenitor of a supernova that had are published in the IVOA Registries, Plane and Bulge (VPHAS+ Public Survey), and previously been imaged in one of the allowing VO tools to discover them. APEXBOL data from the APEX Telescope Large Area 16 non-contiguous VIRCAM detectors), Survey of the Galaxy (ATLASGAL Large Programme). and the ability to find images or source Background imagery is from the DSS. tables in different filter bands whose The Archive Community Forum ­footprints overlap (enabling the selection protocol used to accept the queries and of processed data for colour-magnitude Finally, open communication with users return the results is the Tabular Access studies). is crucial in order to collect precious Protocol (TAP) 16 of the VO. Existing feedback and exchange individual expe­ public domain software libraries providing The tables exposed in this first release riences. To this end, the ESO Archive TAP-client capabilities can be used to of the ESOtap 20 service are the IVOA Community Forum 2 9 is available for implement full programmatic access to Obscore 21 which fully characterises the users to post comments, questions and the ESO science archive (for example, processed products, and ESO tables suggestions addressed to ESO, or inten­ astroquery 17, pyvo 18 , STILTS 19 , to name describing the LPO and Chajnantor raw ded for the community at large. Posts are but a few). observations and atmospheric condi- moderated by ESO and, provided they tions 22, 23, 24 (for example, seeing, precipi- meet basic standards of relevance and The ability to access the archive with table water vapour, isoplanatic angle). etiquette, are made openly visible. scripts allows users to efficiently and reli- A second TAP server 25 is available to ably run long and/or repetitive sequences query the content of more than five billion of queries, such as those needed to records of high-level science catalogue Acknowledgements quickly access data from monitoring or data. In order to optimise the response The first step towards providing this comprehensive other time-critical programmes. The for such a large pool of data, the spatial suite of services involves the curation of archive capabilities of ADQL allow queries on the searches supported in this first release assets, which is an integral part of the Phase 3 pro- spatial footprints of the processed data. are limited to cones. Extensive documen- cess (Arnaboldi et al., 2014). We would like to warmly Some examples of the types of queries tation is provided in terms of practical thank the PIs and their teams who have engaged with us in this process, which has greatly enhanced include searching in a cone, a more examples, which are intended to provide the value of the ESO Science Archive.

6 The Messenger 172 – June 2018 We would like to gratefully acknowledge the very Louys, M. et al. 2017, IVOA Recommendation 14 International Virtual Observatory Alliance (IVOA): fruitful collaboration with Centre de Données Pirenne, B. et al. 1998, The Messenger, 93, 20 http://www.ivoa.net astronomiques de Strasbourg (CDS). This research Romaniello, M. et al. 2016, The Messenger, 163, 5 15 The IVOA Astronomical Data Query Language: has made use of the Aladin sky atlas developed Stoehr, F. et al. 2017, The Messenger, 167, 2 http://www.ivoa.net/documents/latest/ADQL.html at CDS, Strasbourg Observatory, France (Bonnarel Tody, D. et al. 2012, IVOA Recommendation 16 Table Access Protocol TAP v1.0 (Dowler, Rixon & et al., 2000, Boch & Fernique, 2014). Tody 2010): http://www.ivoa.net/documents/ TAP/20100327/ Many crucial aspects of the work presented here Links 17 Astroquery: http://www.astropy.org/astroquery would have not been possible without the results of 18 pyvo: https://pyvo.readthedocs.io/en/latest the sustained, distributed efforts of the VO commu- 1 ESO Science Archive: http://archive.eso.org 19 STILTS: http://www.star.bris.ac.uk/~mbt/stilts nity. The following IVOA standards were used: 2 ESO contributed processed data: http://eso.org/ 20 The ESOtap service: http://archive.eso.org/tap_obs ADQL v2.0, DataLink v1.0, ObsCore v1.1, SSAP v1.1, rm/publicAccess#/dataReleases 21 The IVOA ObsCore data model (Louys et al., TAP v1.0, UWS v1.1 30, DALI v1.1 31, SAMP v1.3. 3 ESO pipeline-processed data: https://www.eso. 2017): http://www.ivoa.net/documents/ObsCore org/sci/observing/phase3/data_streams.html 22 Ambient conditions for Paranal: http://www.eso. We have made use of the taplib library 32 by 4 Report of the ESO Working Group on Science org/asm/ui/publicLog?name=Paranal) Grégory Mantelet (Astronomisches Rechen Institut, Data Management (STC-580): https://www.eso. 23 Ambient conditions for La Silla: http://www.eso. Heidelberg), which is a collection of Java libraries org/public/about-eso/committees/stc/stc-88th/ org/asm/ui/publicLog?name=LaSilla implementing ADQL, TAP, and UWS. Grégory’s public/STC_580_Data_management_working_ 24 Ambient conditions for APEX: http://www.apex- ­support is gratefully acknowledged. The ESO imple- group_report_88th_STC_Meeting.pdf telescope.org/weather mentation of taplib 33, providing additional support 5 TOPCAT is accessible at: http://www.star.bris. 25 ESOtap server to catalogue data: http://archive. for the specific Microsoft-SQL Server geographical ac.uk/~mbt/topcat eso.org/tap_cat datatypes and functions, and the implementation 6 Aladin and AladinLite: http://aladin.u-strasbg.fr 26 Programmatic and tool access demonstration of the SSA protocol 34, are made available to the 7 The ESO Archive Science Portal: http://archive. page: http://archive.eso.org/programmatic community via github. eso.org/scienceportal 27 IVOA DataLink v1.0 (Dowler et al., 2015): http:// 8 CDS Sesame service: http://cds.u-strasbg.fr/ www.ivoa.net/documents/DataLink/index.html cgi-bin/Sesame 28 VO SSAP (Tody et al., 2012): http://www.ivoa.net/ References 9 The IVOA Simple Application Messaging Protocol documents/SSA/20120210/REC-SSA-1.1- (SAMP): http://www.ivoa.net/documents/ 20120210.htm Arnaboldi, M. & Retzlaff, J. 2011, The Messenger, SAMP/20120411/REC-SAMP-1.3-20120411.html 29 ESO Archive Community Forum: 146, 45 10 Wikipedia definition of faceted search: https://esocommunity.userecho.com Arnaboldi, M. et al. 2014, The Messenger, 156, 24 https://en.wikipedia.org/wiki/Faceted_search 30 IVOA standards: http://www.ivoa.net/documents/ Boch, T. & Fernique, P. 2014, ADASS XII, ed. Manset, 11 HEALpix data analysis and visualisation software: UWS/20140527/WD-UWS-1.1-20140527.html N. & Forshay, P., ASP Conf. Series, 485, 277 http://healpix.sourceforge.net 31 DALI: http://www.ivoa.net/documents/DALI/ Bonnarel, F. et al. 2000, A&AS, 143, 33 12 The hierarchical tiling mechanism HiPS, devel- 32 taplib: https://github.com/gmantele/taplib Dowler, P., Rixon, G. & Tody, D. 2010, oped by the CDS: http://aladin.u-strasbg.fr/hips 33 ESO implementation of tablib (G.Mantelet): IVOA Recommendation 13 Programmatic and tool access overview: https://github.com/vforchi/taplib Dowler, P. et al. 2015, IVOA Recommendation http://archive.eso.org/cms/eso-data/programmatic- 34 ESO implementation of SSA on github: access.html https://github.com/vforchi/SSAPServer ESO/Juan Carlos Muñoz

The final image taken by VIMOS before it was decommissioned on 24 March 2018 was of the interacting galaxies NGC 5426 and NGC 5427, which form Arp 271.

The Messenger 172 – June 2018 7 Telescopes and Instrumentation DOI: 10.18727/0722-6691/5074

HAWK-I/GRAAL Science Verification

Bruno Leibundgut 1 Proposal solicitation and submission onds). The image quality throughout was Pascale Hibon 1 quite good (0.5 arcseconds), and nearly Harald Kuntschner 1 The call for HAWK-I/GRAAL Science Veri- independent of the outside seeing with Cyrielle Opitom 1 fication proposals and the corresponding occasionally spectacular image quality in Jérôme Paufique 1 web page were published on 2 October the fast photometry mode (0.2 arcsec- Monika Petr-Gotzens 1 2017 1. The call was announced through onds in K). In rare cases, an elongation Ralf Siebenmorgen 1 the ESO Science Newsletter on 17 Octo- of the images was observed, which was Elena Valenti 1 ber 2017 2 with a deadline for proposal probably not related to the adaptive Anita Zanella 1 submission of 31 October 2017. Nineteen optics, as it has also been observed with proposals were received by the deadline other instruments on UT4. The only notice- and evaluated by the Science Verification able instrument issue during the run was 1 ESO team over the following 2.5 weeks. A total a systematic instrument configuration allocation of 35.5 hours was chosen, a tool error, revealed for non-zero position slight oversubscription compared to the angles and corrected during the run. Science Verification observations with available observing time (30 hours in total the High Acuity Wide field K-band over four summer nights). This resulted The observations essentially followed the Imager (HAWK-I) instrument enhanced in 14 projects being selected for schedul- priority given by the ranking of the pro- by the ground-layer adaptive optics ing. All Principal Investigators (PIs) were posals. The seven top-ranked projects module (GRAAL) were obtained during informed of the outcome of this selection were completed fully within the requested 4.5 nights from 2 to 6 January 2018. process on 27 November, and the constraints. Some data were obtained Fourteen projects were selected from a ­successful applicants were given a dead- for three programmes, and for one pro- total of 19 submitted proposals. The line for submission of the Phase 2 material ject, the data did not comply within the total time scheduled for these 14 pro- of 14 December 2017. All PIs complied requested constraints. The lowest-ranked jects was 35.5 hours, which represents with this deadline and the submitted three projects could not be started. a slight oversubscription for the four material was verified by the User Support allocated summer nights. The seven top- Department before 22 December, so ranked projects were completed, three the HAWK-I/GRAAL Science Verification Archive and data processing more programmes received some data, queue was ready by 31 December. one was observed outside the requested All raw and pipeline-reduced data are constraints, and three projects were not The scheduled projects covered a range publicly available through the ESO science started. The Science Verification nights of topics, including: the characterisation archive. The ESO data quality control­ were affected by various technical of a Solar System binary object — the group reduced all Science Verification problems, mostly unrelated to GRAAL, dwarf planet Eris and its moon Dysnomia; data and the resulting products are avail- which resulted in a total loss of 10 hours. observations of the mass function and able from the ESO Phase 3 data product Half a night was allocated on 6 January dynamics of young clusters; pairs of stellar form 3. A new version of the HAWK-I/ to compensate for some of the lost time. clusters and their origins; and a massive GRAAL data reduction pipeline has been The atmospheric conditions were rather embedded cluster. Star formation projects released. The HAWK-I/GRAAL Science variable with occasionally excellent included an investigation into the infrared Verification web page also contains direct ­natural seeing (0.3 arcseconds). The excess emission of pre-main-­sequence links to the Science Verification data in ground layer turbulence fraction varied stars in the Large Magellanic Cloud (LMC) the archive 1. from 40% to 85% during these nights. and observations of molecular hydrogen The best performance in terms of in a Herbig Haro object. Extragalactic improved image quality was observed topics included a potentially binary active Some early science results when the ground layer fraction was galactic nucleus in a merging galaxy sys- above 70%, as expected for the system. tem, and multi-epoch observations of Solar System objects: Eris and The image quality in the K filter ranged luminous infrared galaxies to search for Dysnomia between 0.2 arcseconds (in excellent core-collapse supernovae. Trans-Neptunian objects (TNOs) are icy/ conditions) to about 0.5 arcseconds (with rocky bodies located beyond the orbit mediocre seeing, > 0.8 arcseconds), of Neptune, which are believed to be rem- and a small fraction of ground-layer tur- Observations nants of the building blocks from which bulence. The delivered image quality planets formed. The dwarf planet was very stable, but in some cases an All observations were made without tip- (136199) Eris is one of the largest TNOs asymmetric point spread function was tilt stars and using only the four laser known in the Solar System, with a size observed. beacons provided by the Adaptive Optics similar to that of Pluto. During the HAWK-I/ Facility (AOF). Various technical problems GRAAL Science Verification, high-­ led to a loss of several hours during the precision photometric­ observations of Eris Science Verification nights. At the same were obtained at near-infrared wave- time some very good seeing conditions lengths. The aim of the observations was were encountered (down to 0.3 arcsec- to characterise the surface heterogeneity

8 The Messenger 172 – June 2018 Figure 1. One of several Probing the cores of nearby stellar images of Eris in one clusters HAWK-I quadrant with a 3.6 × 3.6 arcminute field The mass function and the dynamics of of view. young clusters are among the most important observational constraints to the study of star formation. The presence of extremely bright, massive stars has prevented the analysis of environments in the cores of stellar associations. The γ Velorum cluster, which has an age of Cyrielle Opitom, Akhil Gunessee, Pascale Hibon Pascale Gunessee, Akhil Opitom, Cyrielle ~ 7 Myr and is at a distance of 350 pc, was targeted with HAWK-I/GRAAL spe- cifically to observe the region around the naked-eye star γ Velorum (V = 1.8 mag). The star itself was carefully positioned outside the HAWK-I field of view and ERIS observations were obtained in the fast-­ photometry mode (integration time ~ 3.3 seconds, see Figure 2). This resulted

in 2000 individual frames in Ks and 1040 frames in Y. A few frames with elongated images were discarded in the analysis. These data will ultimately provide a colour- magnitude diagram that will probe the stars down to about 5 Jupiter masses in of this large TNO and detect photometric seconds. A total of 18 high-quality images the core of the cluster. variations due to its rotation. Thanks to the were obtained, spread over three con- performance of the GRAAL AO module secutive nights. If photometric variations (Figure 1), the team should be able to re­ are detected in these observations, it will Figure 2. A comparison of HAWK-I/GRAAL images with archival VISTA observations around the star solve Eris and its moon Dysnomia, whose provide a way to definitively determine the γ Velorum. The circles mark the sources detected in separation varies between 0.3 and 0.5 arc­ rotation period of the dwarf planet Eris. the HAWK-I frames.

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40.0ೀ 40.0ೀ

21ಿ00.0ೀ 21ಿ00.0ೀ

42.00s 40.00s 38.00s 8h09m36.00s 42.00s 40.00s 38.00s 8h09m36.00s Right ascension (J2000) Right ascension (J2000)

The Messenger 172 – June 2018 9 Telescopes and Instrumentation Leibundgut B. et al., HAWK-I/GRAAL Science Verification

Figure 3. HH 212 in the

H2 filter at 2.12 μm with HAWK-I/GRAAL. The image shown here is 5 by 1.5 arcminutes. Christian Schneider Christian

Stellar outflows from young stars Young star cluster RCW38 early evolution of stars in such an Herbig-Haro objects are massive outflows RCW 38 is the youngest (< 1 Myr) of the environment. driven by stellar systems in the making. Milky Way’s 13 super star clusters (Fukui They are large objects on the sky, extend- et al., 2016), and the densest stellar sys- Stellar cluster pairs in the LMC ing over several arcminutes (~ 1 parsec), tem within 4 kpc of the Sun (Kuhn et al., The LMC possibly hosts the largest and appear mostly diffuse, although they 2015). The cluster contains hundreds of ­number of candidate stellar cluster pairs also contain point-like ­substructures, protostars, pre-main sequence stars, and within the Local Group. These systems which evolve on timescales of years. In OB-star candidates (Winston et al., 2011), are extremely interesting as their study fact, time evolution is key to understand- along with a substantial substellar candi- can provide a fresh look at the mecha- ing the physics of outflows, and in par- date population revealed in the cluster nisms of cluster formation and evolution. ticular the link to their driving source: the core (Muzic et al., 2017). With HAWK-I/ As part of a larger effort aimed at provid- planet-forming young stellar disc. Efficient GRAAL data (see the cover image), one ing an independent characterisation of mapping of Herbig-Haro objects requires can directly study several key aspects of cluster pairs in the LMC (Dalessandro et wide-field, high-­spatial-resolution data; star formation: massive star birth; low- al., 2018; Mucciarelli et al., 2012) this this is exactly what HAWK-I provides in mass star and brown dwarf formation in a study exploited the wide field of view and the near-infrared, where extinction effects dense environment and under the influ- the enhanced spatial resolution available are mitigated. Molecular hydrogen emis- ence of photoionisation fronts from mas- with HAWK-I/GRAAL to observe the clus- sion at 2.12 μm was observed in the sive stars; the initial mass function (IMF) ter pair NGC 2136 and NGC 2137 in the ­Herbig-Haro object HH 212 using HAWK-I on an unprecedented sample spanning J- and H-bands. The high-quality colour-­ in 2007. The driving source of HH 212 three orders of magnitudes in mass; and magnitude diagrams for the two clusters is a low-mass protostar located in the mass segregation in young clusters. (Figure 5) will yield accurate cluster ages Orion star-forming region at a distance of from the main-sequence turnoff luminosity, about 400 pc. The new HAWK-I/GRAAL Star-forming complex in the LMC the structure of the systems from accurate Science Verification image of HH 212 Pre-main-sequence candidate stars in star counts, and density profiles and the shows all the characteristics of Herbig-­ the LMC often show near-infrared degree of mutual interaction. This informa- Haro objects: well developed bow excesses compared to theoretical model tion will, in turn, yield clues as to the origin shocks, where the outflowing gas inter- predictions. This was discovered using and final fate of these stellar systems. acts with the ambient medium; jet-like VISTA images from the VISTA Magellanic features closer to the source, tracing the Cloud survey (VMC; Cioni et al., 2011). Supernovae in the cores of galaxies largely undisturbed flow originating in However, the VISTA images are affected Luminous infrared galaxies are highly the star-disc system; and structure at by crowding and photometric uncertain- star-forming and dust-obscured galaxies. essentially all scales. The new data (Fig- ties, which could also mimic this excess. While relatively rare in the local Universe, ure 3) compared with the archival HAWK-I The HAWK-I/GRAAL Science Verification they start to dominate the total core-­ image will enable proper motions to be observations targeted the central area collapse supernova rates at z ~ 1. Two measured with high accuracy, i.e., down of the star-forming complex N44 to obtain luminous infrared galaxies were observed to 20 km s–1, over the entire length of a colour-magnitude diagram to well during HAWK-I/GRAAL Science Verifica- HH 212 — a fraction­ of the typical flow below 1 solar mass. The increased angu- tion. This resulted in the discovery of a velocity of 300 km s–1. A detailed com- lar resolution has resolved the crowding new supernova, SN 2018ec (Kankare et parison between the dynamics of the problem — almost 3 times as many al., 2018; Figure 6), in NGC 3256, which blue- and red-shifted lobes is especially stars were detected in the densest young is only the second reported supernova interesting because, although HH 212 star cluster areas (Figure 4) — and also in this luminous infrared galaxy, with an appears symmetrical, its lobes show sub- helped with independent photo­metry. If expected intrinsic core-collapse super- stantially different space velocities, some- the near-infrared excess persists in these nova rate of about one per year. Optical thing that is challenging to explain with HAWK-I/GRAAL data as well, then it may transient surveys did not discover this current jet launching models. be that the low metallicity in the LMC is nearby supernova — at a distance of only responsible for significant changes in the 37 Mpc — owing to a combination of

10 The Messenger 172 – June 2018 Figure 4. Comparison of HAWK-I/ GRAAL (left) and VISTA (right) images of a region in the N44 star forming

Viktor Zivkov complex in the LMC.

10 arcseconds 10 arcseconds

Figure 5. J and H colour-composite image of the binary cluster pair NGC 2136 and NGC 2137. The image size is 210 × 160 arcseconds. Emanuele Dalessandro Emanuele

the high extinction (AV ~ 2 magnitudes) A dual active galactic nucleus? nucleus system are crucial to character­ along the line of sight of the host galaxy Recent observations using the VLT instru- ising the coordinated assembly of the and the high background. SN 2018ec ment Multi Unit Spectroscopic Explorer ­galaxies and the supermassive black

was classified as a Type I c supernova by (MUSE) uncovered a potential dual active holes. The goal of obtaining the Ks-band the survey “extended-Public ESO Spec- galactic nucleus candidate at redshift image (Figure 7) was to detect the host troscopic Survey for Transient Objects” z = 3.3 with a separation of only 20 kpc. galaxy of the obscured active galactic (ePESSTO; Berton et al., 2018). The study The merging of supermassive black nucleus. Indeed, the host galaxy was of SN 2018ec will contribute to the long- holes in galaxy mergers is expected in detected at the expected location (thanks term aim of deriving missing fractions for the hierarchical­ formation of galaxies. to the exquisite image quality, of 0.4 arc­ core-collapse supernovae from the local HAWK-I/GRAAL follow-up observations seconds, and depth delivered by the to the high-redshift Universe. of this high-redshift dual active galactic adaptive optics system). After de-blending

The Messenger 172 – June 2018 11 Telescopes and Instrumentation Leibundgut B. et al., HAWK-I/GRAAL Science Verification

Figure 6. Discovery the quasar plus companion galaxy sys- image of supernova tem using the software package GALFIT3 SN 2018ec in NGC 3256 (Peng et al., 2010), Ks-band magnitudes Erkki Kankare Erkki in a Ks image. of 19.2 (Vega magnitudes) for the quasar host galaxy and 20.6 magnitudes for the companion galaxy were derived. At

z = 3.3 the Ks-band corresponds nearly to the rest-frame velocity, and stellar masses of log(M /M ) ~ 11.4 and ~ 10.9 ∗ ⊙ were derived for the quasar host and the companion, respectively (adopting a mass-to-light ratio of ~ 0.1 for a 200 Myr- old stellar population). The host galaxies are both very massive and probably trace one of the most massive dark matter halos at that epoch of the Universe (Husemann et al., 2018).

Acknowledgements

The team received extensive support from the Paranal staff for these Science Verification observa- tions, in particular from Israel Blanchard and Sergio 10 arcseconds Vera, who supported the observations, Johann Kolb, who made sure GRAAL worked, and Philippe Duhoux for the software support. The team would also like to thank the Day Shift Coordinator on duty during this run for their support. 22 4 )

–2 We are grateful to Hervé Bouy, Christian Schneider, Jil 21 Kora Muzic, Viktor Zivkov, Emanuele Dalessandro, csec Bernd Husemann Bernd Erkki Kankare and Bernd Husemann, who kindly 2 ar

s) QSO Host 20 provided the images of the first HAWK-I/GRAAL a] ­Science Verification results. eg

19 [V 0 s second rc 18 References (a y Δ –2 Berton, M. et al. 2018, The Astronomer’s Telegram, 17 agnitude 11160 (m s

k Cioni, M.-R. et al. 2011, A&A, 527, A116

16 Σ –4 Dalessandro, E. et al. 2018, MNRAS, 474, 2277 Fukui, Y. et al. 2016, ApJ, 820, 26 15 Husemann, B. et al. 2018, A&A, accepted, –4 –2 0 24 –4 –2 0 24 arXiv:1805.09845 Δx (arcseconds) Δx (arcseconds) Kankare, E. et al. 2018, The Astronomer’s Telegram, 11156 Figure 7. Left panel: VLT/HAWK-I/GRAAL Ks-band Mucciarelli, A. et al. 2012, ApJL, 746, 19 image of the LBQS 0302-0019 dual AGN system. Muzic, K. et al. 2017, MNRAS, 471, 3699 Right panel: Same as left, but the quasar light has been subtracted based on the PSF obtained froma nearby star. Significant extended emission is Links detected for the companion galaxy well above the surface brightness limit. The distribution of VLT/ 1 HAWK-I/GRAAL Science Verification web page: MUSE He II emission is shown by green contours. http://www.eso.org/sci/activities/vltsv/ The emission peaks exactly at the location of the hawkigraalsv.html companion galaxy (dubbed “Jil”) with a slight prefer- 2 ESO Science Newsletter dated 17 October 2017: ence towards the fainter asymmetric part of the http://www.eso.org/sci/publications/newsletter/ ­continuum distribution. oct2017.html 3 ESO Phase 3 data product query form for HAWK-I: http://archive.eso.org/wdb/wdb/adp/phase3_ imaging/form?ins_id=HAWKI

12 The Messenger 172 – June 2018 Astronomical Science

Combined observations from MUSE on the VLT (red ring), the Hubble Space Telescope (red and green background) and the NASA Chandra X-ray Observatory (blue-purple) reveal the presence of an isolated neutron star (blue spot at the centre

of the red ring) in the Small Magellanic Cloud. ESO/NASA, ESA and the Hubble Heritage Team (STScI/AURA)/F. Vogt et al.

The Messenger 172 – June 2018 13 Astronomical Science DOI: 10.18727/0722-6691/5075

ALMA Constrains the Stellar Initial Mass Function of Dusty Starburst Galaxies

1, 2 –1 Zhi-Yu Zhang and evolution, such as star formation (for example, in excess of 1000 M⊙ yr , Donatella Romano 3 rates, and the timescales for gas deple- see Ivison et al., 1998) — have their Rob J. Ivison 2, 1 tion and dust formation. ­ultraviolet and optical stellar light heavily Padelis P. Papadopoulos 4, 5 obscured by dust (see Figure 1). How- Francesca Matteucci 6 , 7, 8 ever, according to theories and cosmo- The stellar initial mass function logical simulations, it is in exactly these systems where the most extreme IMF 1 Institute for Astronomy, University of First introduced by Edwin Salpeter variations would arise. Are there any other Edinburgh, Royal Observatory (­Salpeter, 1955), the stellar initial mass sensible, indirect methods to probe the ­Edinburgh, UK function is an empirical probability func- IMF in these important, dust-shrouded 2 ESO tion which describes the relative numbers systems? 3 INAF–Osservatorio di Astrofisica e of stars that form in different mass ranges ­Scienza dello Spazio di Bologna, Italy during a single star formation episode. Luckily, carefully selected chemical 4 Department of Physics, Aristotle Univer- The determination of the shape of the ­abundances (see the next sections) can sity of Thessaloniki, Greece IMF — whether it is constant and universal be measured at millimetre/submillimetre 5 Research Center for Astronomy, or it depends on the physical conditions wavelengths — a regime relatively free ­Academy of Athens, Greece in the interstellar medium (ISM) out of from the pernicious effects of dust; these 6 Department of Physics, University of which the stars form — is of the utmost provide a fossil imprint of the chemical ­Trieste, Italy importance for modern astrophysics, enrichment processes and an indirect 7 INAF–Osservatorio Astronomico di because of its fundamental role in all constraint on the prevailing stellar IMF in ­Trieste, Italy ­theories of star and galaxy formation. those extreme environments. It is well 8 INFN, Sezione di Trieste, Italy known (for example, Tinsley, 1980) that Though neatly defined (more or less) stars in different mass ranges produce from a theoretical point of view (Kroupa, different elements in different proportions The stellar initial mass function (IMF) is 2001), the IMF is not easily derived from and on different timescales, with the fundamental to all measurements of direct star counts (Bastian et al., 2010). ­initial chemical composition of the stars cosmic star formation, which involves Many challenges must be overcome in also playing a role. Indeed, in the last an extrapolation from rare, massive order to convert the observed stellar three decades, systemic variations of the stars (M > 8 M ) to the full stellar mass luminosities into stellar masses, where IMF slope have been explored with the aid ∗ ⊙ spectrum. Classical determinations of uncertainties in stellar distances, ages, of increasingly refined galactic chemical- a galaxy’s IMF are limited to ultraviolet, metallicities, extinctions and the possibility­ evolution models. These attempt to optical and near-infrared wavelengths, of unresolved binary systems severely explain, for instance, the overabundance and these cannot be adopted for dust- hamper our ability to measure the present- of magnesium with respect to iron in local obscured galaxies with intense, ongo- day mass function of a given stellar popu- elliptical galaxies, where magnesium is ing star formation, even in the local lation. Furthermore, the effects of a com- synthesised on short timescales by mas- ­Universe. The unprecedented sensi- plex star formation history and finite stel- sive stars and iron is produced mostly tivity of the Atacama Large Millimeter/ lar lifetimes must be taken into account on long timescales by type I a supernovae submillimeter Array (ALMA) allows us to to recover the IMF from the present-day with relatively low-mass progenitors, or detect weak emission from 13CO and mass function. For example, the more the low metallicities measured in gas-rich, C18O isotopologues, which offer a sen- massive a star, the less time it takes to star-forming dwarf galaxies. However, sitive, relatively dust-free, probe of the evolve off the main sequence; at the same ­differences in star formation timescales IMF. Globally low 13CO/C18O ratios for time, low-mass stars — with lifetimes and/or galactic outflows have sometimes all our targets — dusty starburst galax- comparable to the age of the Universe — shown to act in a similar way, making it ies at redshifts ~ 2–3 — alongside a continue to populate the present-day very difficult to prefer a variable IMF over detailed chemical evolution model imply mass function. This readily introduces a other possibilities (Matteucci, 1994). that stars formed in extreme starburst bias against high-mass objects. environments are significantly biased towards massive stars compared to Carbon, nitrogen and oxygen production ordinary star-forming spiral galaxies. Deducing the shape of the IMF from its in stars, and mixing in the ISM We have combined information from the chemical imprint coldest interstellar medium (at tens The seven stable isotopes of carbon, of Kelvins) with the physics of nucleo- Estimating the IMF directly is therefore nitrogen and oxygen (the CNO elements) synthesis in hot stars (at tens of millions anything but a trivial task. On top of this, are produced solely by nucleosynthesis of Kelvins), to delineate the formation direct observations of stellar light are not in stars. On galactic scales, 13C and 18O and evolution of galaxies.­ This opens up always possible. are released predominately by low- and a new window to probe the stellar IMF intermediate-mass stars (M < 8 M ) and ∗ ⊙ of galaxies with ALMA and it challenges The most massive and luminous galaxies massive stars (M > 8 M ), respectively ∗ ⊙ our understanding of funda­mental that shine at high redshift — for instance, (Kobayashi et al., 2011). This is due to parameters governing galaxy formation those producing stars at tremendous rates the differing energy barriers in nuclear

14 The Messenger 172 – June 2018 Figure 1. Artist’s impressions of a dusty starburst galaxy. The star forma- tion rate is supposedly a few hundred –1 M⊙ yr . The dusty curtain obscures the optical and ultraviolet (and, some- times even the near-infrared) light from stars and only emission at much longer wavelengths, i.e., from submillimetre/ millimetre to centimetre can escape. Classical, direct measurements of the present-day mass function are simply not possible for such galaxies.

reactions and the mass-dependent evo- isotopes. Measurements of 13CO and ALMA observations of 13CO and C18O lution of stars. C18O — isotopologues of carbon towards dusty starbursts ­monoxide, 12C16O or CO — in the ISM 13C is mostly synthesised as a secondary can thus be used to trace the relative Starburst galaxies in the local Universe element, i.e., its production needs the 13C and 18O abundances produced by most likely had prior episodes of cosmo- pre-existing seed of the primary element, successive generations of stars. logical evolution, so the elementary abun- 12C, to be present at a star’s birth. How- dances in their ISM could be affected by ever, 13C also has a primary production In theoretical work by Romano et al. a complex star formation history may not channel, if synthesised directly from 12C (2017), we reassessed the relative roles strictly be related to the current episode produced through helium burning in the of stars in different mass ranges in the of star formation. We selected a sample star itself. This may happen at the base production of the rare CNO isotopes, of dusty starburst galaxies at z ~ 2–3, of the convective envelopes of asymptotic 13C, 15N, 17O and 18O, along with the more with less than 3 Gyr of cosmic time avail- giant branch (AGB) stars going through abundant 12C, 14N and 16O. We used a able for prior episodes of evolution. So periodic episodes of dredge-up (Renzini proprietary galactic chemical evolution they are expected to have relatively clean & Voli, 1981), or in low-metallicity, fast-­ code for the Milky Way and stellar yields and simple star formation histories. rotating, massive stars, in which rotation from the literature for massive stars, AGB Owing to the weakness of the isotopo- triggers the production of primary 13C stars and novae to show that the available logue lines (13CO and C18O), we selected by allowing the diffusion of 12C produced isotopic data for the local ISM, proto-­ the four strongest CO emitters in the liter- in He-burning zones into zones burning solar nebula, metal-poor stars and abun- ature, which are all gravitationally lensed hydrogen (Chiappini et al., 2008). dance gradients across the Galactic systems with their signals amplified by disc can be reproduced satisfactorily factors of ~ 3–10. Massive stars dominate the production of with a suitable choice of yields. Moreover, 18O (Timmes et al., 1995), which is mostly we showed that our models could be We performed simultaneous observations synthesised as a secondary element in extended to constrain the stellar IMF of of 13CO and C18O emission lines, using the early stages of helium burning, start- star-forming galaxies across cosmic time. ALMA in its relatively compact array con- ing from any pre-existing 16O. Therefore Among the remaining uncertainties, an figurations, in the spring of 2015 (Zhang 18O production is strongly dependent on unknown star formation history is particu- et al., 2018). Between 10 and 30 minutes the initial stellar metallicity. larly tricky to deal with. However, if gal­ were spent on each target per observa- axies are caught during the earliest stages tion. We manually calibrated all data These isotopes are then ejected into the of their evolution, the uncertainties are using the Common Astronomy Software ISM via stellar winds, where they form significantly reduced. Applications (CASA) package 1 (v. 4.7.1) molecules in the same way as their major following standard procedures. The final

The Messenger 172 – June 2018 15 Astronomical Science Zhang Z.-Y. et al., ALMA Constrains the Stellar IMF of Dusty Starburst Galaxies

angular resolution spanned 1.6 to –47°23ಿ48.0ೀ 0.56 3.7 arcseconds, corresponding to spatial 13CO J = 3 ൺ 2C18O J = 3 ൺ 2 resolutions of ~ 14–30 kpc at z ~ 2. We 0.58 x flu

) ) 52.0ೀ 0.40 optimised for sensitivity, both in the –1 s line

000 observations and in the data reduction, 2 0.32 ed km

(J so the final images have limited angular 56.0 –1

ೀ 0.24 grat ion t resolution — most targets are unresolved te in beam 0.16 y or only marginally resolved. ty

24 00.0 (J

Declina ಿ ೀ 0.08 loci

Most targeted lines are detected robustly 0.00 Ve with signal-to-noise (S/N) > 5. Only two 04.0 ೀ –0.08 targeted lines are marginally detected 08.00s 07.50s 07.00s 1h25m06.50s07.50s07.00s1h25m06.50s at ~ 4-σ level; J = 3 → 2 from SDP.17b Right ascension (J2000)Right ascension (J2000) (­HATLAS J090302.9–014127) and J = 5 → 4 from SPT 0103–45 (SPT-S Figure 2. Velocity-integrated flux map (zero moment) emission. Black contours show the high-resolution 13 18 J010312−4538.8). However, the high-J of CO and C O for the J = 3 → 2 transition in 336-GHz continuum image, obtained from the SPT 0125–47. White contours show the low-resolution ALMA archive, presenting the Einstein ring structure transitions show consistent results at 94-GHz continuum, tracing the rest-frame cold dust produced by the gravitational lensing effect. higher S/N, so we can be confident about the observed line ratios. See Figure 2 SMC Global ratio or nuclei for an example of our ALMA detections of Discs 13CO and C18O, J = 3 2. → IRAS 13120-5453 centre SMC, LMC, dwarfs LMC IRAS 13120-5453 global SMGs (this work) Literature data on 13CO and C18O in IC 10 ­various galaxies 10 Milky Way, discs, O)

We compiled a collection of line flux 18 arms

13 18 (C ratios from the literature, I( CO)/I(C O) I )/ at the same J transitions, in various types

CO Star-forming nuclei 13 ( of gas-rich galaxies. ­Figure 3 shows the I Mrk 231 SMGs (this work) I(13CO)/I(C18O) ratio as a function of infra- red luminosity, LIR (i.e., the apparent star ULIRGs/SMGs formation rate traced by massive stars). 1

Discs of nearby normal spiral galaxies Arp 220 have I(13CO)/I(C18O) line ratios of ~ 7–10, SMMJ 2135–0102 Resolved starburst similar to that of the Milky Way’s disc (Jiménez-Donaire et al., 2017). Galaxies 8910 11 12 13 14 with extremely high star-forming activity log L (L ) (≥ 100–500 × Milky Way) all have much 10 IR ๬ lower ratios, close to unity (Henkel et al., Figure 3. I(13CO)/I(C18O) as a function of intrinsic al., 2017), local Ultraluminous infrared galaxies 13 18 infrared luminosity (rest-frame 8–1000 μm, L ). Our (ULIRGS; Henkel et al., 2014), a lensed submillimetre 2014). The lowest I( CO)/I(C O) ratio, an IR lensed starburst sample is plotted with red symbols. galaxy (SMG), SMM J2135–0102 (Danielson et al., upper limit of 0.5, is found in a starburst The I(13CO)/I(C18O) measurements of nearby star- 2013), gas-rich dwarf galaxies, the Magellanic knot — the central 500-parsec region forming galaxies, galactic nuclei (Jiménez-Donaire et Clouds (SMC and LMC) and IC 10, are presented for of the nearby ultra-luminous infrared gal- comparison. axy IRAS 13120–5453 (Sliwa et al., 2017). Gas-rich dwarf galaxies, such as the dances are not biased by differential ­systems like the Milky Way. To verify Magellanic Clouds and IC 10, show the astro-chemical effects and differential this, the degeneracy with star formation highest ratios of I(13CO)/I(C18O), greater lensing effects for the bulk of the history needs to be taken into account, than 30. I(13CO)/I(C18O) shows a clear ­molecular gas in galaxies. So the line because the lifetimes of stars can also 13 18 decreasing trend with LIR, or the apparent ratio of I( CO)/I(C O) can be used bias the final abundances in the ISM. star formation rate traced by massive safely to trace the abundance ratio of stars. 13CO/18O in the ISM. Galactic chemical evolution Both the 13CO and C18O lines are excited Such a systematic variation of isotopo- predominantly by collisions with H2 mole- logue abundance ratios over galaxy-sized How much variation does the star forma- cules, so they share identical excitation molecular hydrogen reservoirs indicates a tion history induce in the 13C/18O ratio, conditions. These lines are optically thin, change of the stellar IMF from the canoni­ compared to any changes due to varia- given their low abundances. Their abun- cal one found in normal star-forming tions of the IMF slope? To answer this

16 The Messenger 172 – June 2018 Redshift, z Figure 4. Evolutionary tracks of 13C/18O abundance 5 4 3 2 1 0 ratio in the ISM, using various IMFs. Coloured lines 1000 correspond to different IMFs. a) Modelled starburst IMF ) a history, which started evolving 2 Gyr after the –1 Bottom-heavy r 100 11 Big Bang, grew to a total stellar mass of 10 M⊙ y Kroupa ๬ and stopped forming stars 1 Gyr later. SFR is the

M 10 Top-heavy star formation rate. b) Corresponding 13CO/C18O (as

R ( Ballero 13 18 1 a proxy of C/ O) abundance ratio as a function SF of redshift, following different IMFs. Our lensed star- burst sample is plotted with red symbols. Blue dots show the 13CO/C18O ratios measured in a few b representative local galaxies. 100 SMC SMC, LMC, dwarfs O

18 LMC C/

13 Milky Way 10 Milky Way, discs NGC 6946 disc arms from massive stars using an assumed

O) ≈ NGC 6946 nuc SMGs (this work) Star-forming nuclei IMF. These need to decrease by a factor 18 Arp220

(C of at least a few, and the gas-depletion I 1 IRAS 13120-5453 avg )/ ULIRGs/SMGs times must then increase by the same SMM J2135-0102 IRAS 13120-5453 nuc CO

13 factor. As a result, most ­fundamental ( I 0.1 Resolved knots parameters in the field of galaxy forma- tion and evolution must be re-addressed, exploiting advances in stellar physics. 246810 12 Hubble time (Gyr) question, we adopt a galactic chemical IMF can reproduce the I(13CO)/I(C18O) Acknowledgements evolution model that accurately includes observed in starburst galaxies, near and Zhi-Yu Zhang, Rob J. Ivison and Padelis P. 13 18 the isotopic yields across the full range far. The extremely low I( CO)/I(C O) ratio ­Papadopoulos acknowledge support from the Euro- of stellar mass, taking into account the measured in the centre of IRAS 13120– pean Research Council in the form of the Advanced differential release of different elements 5453 can be explained with the top- Investigator Programme, 321302, COSMICISM. This into the ISM as a function of a star’s life- heavy and the Ballero­ IMF (Ballero et al., research was supported by the Munich Institute for Astro- and Particle Physics (MIAPP) of the German time, and the initial metallicity, as well 2007), which could reproduce the chemi- Research Foundation (DFG) cluster of excellence as any prior galactic evolution. We have cal abundances of stars in the Galactic “Origin and Structure of the Universe”. This work also benchmarked the model against the rich bulge. benefited from the International Space Science Insti- isotopic datasets of the Milky Way and tute (ISSI) in Bern, thanks to the funding of the team “The Formation and ­Evolution of the Galactic Halo” shown it can reproduce the Galacto­ (Principal Investigator Donatella Romano). This paper centric gradients of isotopic abundance Outlook and implication makes use of ALMA data. ratios, and all the relevant local disc data (Romano et al., 2017). Our results — finding a top-heavy IMF in References dusty starburst systems across cosmic With such a well-calibrated model, we time, where classical IMF measurement Ballero, S. K. et al. 2007, A&A, 467, 123 can safely build up an extreme case for methods cannot be applied — are con- Bastian, N., Covey, K. R. & Meyer, M. R. 2010, the evolution of the 13C/18O abundance sistent with the results from other, less ARA&A, 48, 339 Chiappini, C. et al. 2008, A&A, 479, L9 ratio for a pure starburst, as shown in dusty, less extreme starburst systems, Danielson, A. L. R. et al. 2013, MNRAS, 436, 2793 Figure 4. To do that, we evolve a galaxy such as ultra-compact dwarf galaxies, Henkel, C. et al. 2014, A&A, 565, A3 from z ~ 3 (2 Gyr after the Big Bang) for progenitors of early-type galaxies, and Ivison, R. J. et al. 1998, MNRAS, 298, 583 a span of 1 Gyr, with a high star formation compact starbursting stellar associations Jiménez-Donaire, M. J. et al. 2017, ApJL, 836, L29 Kobayashi, C., Karakas, A. I. & Umeda, H. 2011, rate, until it reaches a total stellar mass of in the Large Magellanic Cloud. MNRAS, 414, 3231 11 10 M⊙. Star formation is stopped com- Kroupa, P. 2001, MNRAS, 322, 231 pletely after that, and the relic evolves The systematic variation of the IMF in Matteucci, F. 1994, A&A, 288, 57 passively to z ~ 0. This model was ­different galaxy types has an obvious Renzini, A. & Voli, M. 1981, A&A, 94, 175 Romano, D. et al. 2017, MNRAS, 470, 401 repeated with four different types of IMF, dependency on their star formation Salpeter, E. E. 1955, ApJ, 121, 161 from bottom-heavy (biased towards low- ­properties. The IMF can no longer be Sliwa, K. et al. 2017, ApJL, 840, L11 mass stars) to top-heavy (biased towards assumed to be universal, with a constant Timmes, F. X., Woosley, S. E. & Weaver, T. A. 1995, massive stars), including the canonical canonical form, as commonly applied in ApJS, 98, 617 Tinsley, B. M. 1980, Fundamentals of Cosmic Kroupa IMF that can reproduce average most cosmological simulations. More­ Physics, 5, 287 Galactic conditions (­Kroupa, 2001). over, all measurements of cosmic star Zhang, Z.-Y. et al. 2018, Nature, DOI: 10.1038/s41586- formation rate and stellar mass, and their 018-0196-x With the Kroupa IMF, the evolved 13C/18O derivatives, must be re-assessed urgently. ratio reaches the range observed in the For example, the star formation rates in Links discs of the Milky Way and nearby normal starburst galaxies are derived from classi- spiral galaxies. However, only a top-heavy cal tracers, which extrapolate observables 1 CASA software: https://casa.nrao.edu/index.shtml

The Messenger 172 – June 2018 17 Astronomical Science DOI: 10.18727/0722-6691/5076

MIKiS: the ESO-VLT Multi-Instrument Kinematic Survey of Galactic Globular Clusters

Francesco R. Ferraro 1, 2 black holes in star clusters can finally Thus, despite its importance, our empiri- Alessio Mucciarelli 1, 2 be addressed, impacting our under- cal knowledge of globular cluster internal Barbara Lanzoni 1, 2 standing of the formation and evolution- kinematics from the very centre (where Cristina Pallanca 1, 2 ary processes of globular clusters and the most interesting dynamical phenom- Livia Origlia 2 their interactions with the Galactic tidal ena occur) to the tidal radius (where the Emilio Lapenna 1, 2 field. effects of the Galactic tidal field are visible) Emanuele Dalessandro 2 is still critically inadequate. In particular, a Elena Valenti 3 detailed knowledge of the velocity disper- Giacomo Beccari 3 Galactic Globular Clusters are gas-free sion profile and the (possible) rotation Michele Bellazzini 2 stellar systems, made up of a few times curve is still missing in the majority of the Enrico Vesperini 4 105 stars of different masses (typically cases. This is essentially due to observa- 5 Anna Lisa Varri from ~ 0.1 to 0.8 M⊙). They are the tional difficulties. Antonio Sollima 2 most populous, and the oldest stellar systems in which stars can be individually In principle, velocity dispersion and observed. Moreover they are the sole ­rotation can be obtained from different 1 Dipartimento di Fisica e Astronomia, cosmic structures that, within the times- approaches. In practice, however, the Università degli Studi di Bologna, Italy cale of the age of the Universe, undergo standard methodology commonly used in 2 INAF–Osservatorio di Astrofisica e nearly all of the physical processes known extra-galactic astronomy (i.e., measuring ­Scienza dello Spazio di Bologna, Italy in stellar dynamics. Galactic globular radial velocities from Doppler shifts and 3 ESO clusters are true touchstones for astro- velocity dispersions from the line broad- 4 Department of Astronomy, Indiana physics. The study of their stellar popula- ening of integrated-light spectra) can ­University, Bloomington, USA tions is crucial to validating predictions ­suffer from severe shot-noise bias in 5 Institute for Astronomy, University of from stellar evolution theory, and they are Milky Way globular clusters, because the Edinburgh, Royal Observatory, UK invaluable laboratories for multi-body acquired spectrum can be dominated by dynamics. Surprisingly, while remarkable the contribution of just a few bright stars progress has been made in the study (for example, Dubath et al., 1997). In the Globular clusters are collisional systems, of Galactic globular cluster stellar­ popu­ case of resolved stellar populations, a where stars of different masses orbit lations (see Carretta et al., 2009 and safer approach is to determine velocity and mutually interact. They are the best Piotto et al., 2015), the kinematical charac- dispersion and rotation from the veloci- “natural laboratories” in the Universe terisation of these systems is just in its ties of individual stars. By combining for studying multi-body dynamics and infancy and the modelling often relies on the line-of-sight information (measured their (reciprocal) effects on stellar evolu- a set of over-simplified assumptions. through resolved spectroscopy) with the tion. Although these objects have been two velocity components on the plane studied since the very beginning of In general, globular clusters are assumed of sky (from internal proper motions), a modern astrophysics, little is known to be quasi-relaxed, non-rotating stellar full 3D view of the velocity space of the observationally about their internal kine- systems, characterised by spherical system can be obtained. This begins to matics, thus preventing a complete ­symmetry and orbital isotropy, with struc- be feasible in Galactic globular clusters. understanding of their dynamical state, tural and kinematical properties (surface and of their formation and evolutionary brightness and velocity dispersion pro- Internal proper motions require high-­ history. We present the first results from files) that are well captured by a truncated precision photometry and astrometry on the Very Large Telescope (VLT) Multi- Maxwellian distribution function (for relatively long time baselines. These are Instrument Kinematic Survey of Galactic example, King, 1966). However, growing finally achievable thanks to multi-epoch globular clusters (MIKiS), which is spe- observational evidence demonstrates HST and Gaia observations. The former cifically designed to provide line-of-sight that although this scenario is correct to are providing the necessary information velocities of hundreds of individual a first approximation, it is largely over- on the centres of Galactic globular clus- stars over the entire radial extension simplified. Indeed, there is accumulating ters (even if the innermost regions of the of a selected sample of clusters. The evidence of significant deviations from densest systems might still be missed; survey allows the first kinematical sphericity (Chen & Chen, 2010), and from for example, see Bellini et al., 2014 and exploration of the innermost regions of a King density profile, a profile used to Watkins et al., 2015 for recent results). In high-density globular clusters. When fit the observed distribution of stars within the meantime, Gaia is providing the com- combined with proper motion measure- a globular cluster as a function of their plementary measures in the outskirts. ments, it will provide the full 3D view in distance from the centre (see Carballo- The line-of-sight kinematical information velocity-space for each system. Long- Bello et al., 2012; Lane et al., 2010). Sig- over the entire radial extension of Galactic running open issues, such as the accu- natures of systemic rotation and pressure globular clusters is still largely missing, rate shapes of the velocity dispersion anisotropy have been detected in several because it requires the collection of large profiles, the existence of systemic rota- clusters (for example, Watkins et al., 2015; samples of individual stellar spectra, both tion and orbital anisotropy (and thus Kamann et al., 2018; and references in highly crowded regions — the central the level of relaxation), and the contro- therein). density of the Milky Way globular clusters 5 –3 versial presence of intermediate-mass can reach up to 7 × 10 L⊙ parsec (see

18 The Messenger 172 – June 2018 Harris, 1996 and 2010) — and over large cally sample the spatial distribution of size of 0.2 arcseconds each. We have sky areas (from 20–40-arcminute diameter stars (which is necessary to properly used the YJ grating covering the 1.00– and even more). This is conceptually easy construct the rotation curve) we 1.35 μm spectral range at a resolution but operationally challenging and requires planned a mosaic of between 4 and 9 R = 3400. This instrument setup is a lot of telescope time. To fill this gap in pointings in the 125-millarcsecond especially effective at simultaneously globular cluster studies and overcome mode (125 × 250 milliarcseconds/pixel, measuring a number of reference these difficulties, we recently conducted 8 × 8 arcseconds field of view). In the ­telluric lines in the spectra of giant a spectroscopic campaign based on densest clusters, an additional central stars for an accurate calibration of the a synergic use of three different VLT pointing was also planned in the radial velocity, despite the relatively facilities. 50-milliarcsecond mode (50 × 100 milli- low spectral resolution. Typically, 7–8 arcseconds/pixel, 3 × 3 arcseconds pointings have been secured in each field of view). With the selected setup cluster. We selected red giant targets The survey (K grating, R = 4000), radial velocities with J < 14, with no stars brighter than can be properly measured from molec- J = 15 within 1 arcsecond from their The Multi-Instrument Kinematic Survey ular CO bandheads in the coolest centre. In order to minimise the effects of Galactic globular clusters (hereafter the giants (Teff < 5000 K) and from some of possible residual contamination MIKiS survey; Ferraro et al., 2018) has atomic lines in the warmer stars. Note from nearby stars and/or from the been specifically designed to provide the that, in the MIKiS approach, integral- unresolved stellar background, the velocity dispersion and rotation profiles field spectroscopy is used in a non- 1D spectra were extracted manually by of a representative sample of Milky Way conventional way; instead of using inte- visually inspecting each IFU and select- globular clusters over their entire radial grated-light spectra at various distances ing the brightest spaxel corresponding extension. With this aim, it takes advan- from the cluster centre, we extract the to each target star’s centroid. Normally, tage of the specific characteristics of spectrum of each distinguishable indi- one star was measured in each IFU three different instruments installed at the vidual star from the most exposed spa- though in a few cases two or more VLT, allowing multi-object spectroscopy tial pixel (spaxel) corresponding to the resolved stars were clearly distinguish- with the appropriate angular resolution, star centroid in the data cube. Typically able in a single KMOS IFU (see Figure 2), depending on the radial region surveyed. several dozens of giants have been and their spectra were extracted. The survey is based on two ESO Large observed down to K ~ 15 in each Programmes (193.D-0232 using the ­cluster with the planned mosaics (see 3. Wide-field multi-object spectroscopy K-band Multi-Object Spectrograph Figure 1). with FLAMES. This has been exploited [KMOS] and the Fibre Large Array Multi to sample the external cluster regions, Element Spectrograph [FLAMES], and 2. Seeing-limited observations with the i.e., out to several arcminutes. We used 197.D-0750 using SINFONI; Principal multi-integral-field spectrograph FLAMES in the combined GIRAFFE- Investigator Francesco Ferraro) and has KMOS MEDUSA mode, which consists of 132 been designed with the core scheme These observations have been per- described below. formed for an optimal coverage of the intermediate radial range (a scale Figure 1. Left panels: Comparison between a recon- 1. Diffraction-limited integral-field of tens of arcseconds). KMOS is a structed SINFONI image and an HST/ACS-HR C ­spectroscopy with adaptive-optics- spectrograph equipped with 24 deploy- image of the innermost 3 × 3 arcseconds of NGC 6388. Each SINFONI spaxel provides a spec- assisted SINFONI able integral-field units (IFUs) that can trum. The red crosses correspond to the stellar These observations are used to resolve be allocated within a 7.2-arcminute ­centroids identified from the HST image; 52 individual stars in the innermost few arcseconds diameter field of view. Each IFU covers RVs have been measured within 1.5 arcseconds of the highest-density clusters. We a ­projected area on the sky of about from the cluster centre. Right panels: The same in the case of NGC 2808, where 700 individual spectra adopted the SINFONI­ K-band grating to 2.8 × 2.8 arcseconds, sampled by an of resolved stars were extracted within 10 arcsec- achieve high Strehl ratios. To symmetri- array of 14 × 14 spaxels with an angular onds from the centre.

HST/ACS-HRC SINFONI

N

E

The Messenger 172 – June 2018 19 Astronomical Science Ferraro F. R. et al., MIKiS

Figure 2. The map in the upper panel shows the location of the targets observed with KMOS in NGC 6388. Lower panel: reconstructed images for 20 IFUs in a typical pointing.

deployable fibres that can be allocated within a 25-arcminute diameter field of view. The adopted HR 21 grating setup, with a resolving power R = 16 200 and spectral coverage from 8484 to 9001 Å, samples the prominent Ca II triplet lines, which are excellent features from which to measure radial velocities. The selected targets are essentially red giant branch stars brighter than I = 18.5. In order to avoid spurious contamination from other sources within the fibres, only isolated stars with no bright neighbours within 2 arcseconds from each target were selected. On average, 3–4 pointings were performed in each cluster.

This approach was first tested, as a proof of concept, on the Galactic globular clusters NGC 6388 (Lanzoni et al., 2013, ­Lapenna et al., 2015) and NGC 2808 (see Figures 1 and 2). Then, for the MIKiS ­survey we selected 30 massive globular clusters across the entire Galaxy (Fig- ure 3), sampling both the bulge/disc stel- lar populations close to the Galactic plane (at z < 1.5 kpc) and the halo ones (at 1.5 < z < 13 kpc).

The targets properly map the parameter space most sensitive to the internal dynamical evolution of the cluster, cover- ing a wide range of central densities and concentration parametersa (2.5 < c < 0.5), and sampling all the stages of dynamical evolution, including both pre- and post- core-collapse globular clusters (with 2.5 a core relaxation time spanning almost 10 3 orders of magnitude). For a reliable determination of the line-of-sight velocity 2 dispersion profile the selected globular clusters are also populous enough (i.e.,

more luminous than MV = –6.5) to provide z 0 c 1.5 large samples of giant/sub-giant stars. To measure stars along a relevant portion

1 Figure 3. Distribution of the targets selected for the –10 MIKiS survey (large circles) showing the height on 0.5 the Galactic plane z vs. absolute integrated V-band magnitude MV (left) and the King concentration parameter c vs. core relaxation time t (right). The –7 –8 –9 789 c total Galactic globular cluster population is also M log t (years) V c ­plotted for reference (small dots).

20 The Messenger 172 – June 2018 Figure 4. Velocity dispersion profiles of NGC 6388 15 NGC 6388 NGC 2808 and NGC 2808 obtained from the radial velocities of individual stars (blue circles) measured following our multi-instrument approach: SINFONI+KMOS+- FLAMES. The number of individual spectra measured 20 with each instrument is labelled. The empty triangles­

) ) 10 in the left-hand panel show the velocity dispersion –1 –1 s s profile obtained from integrated-light spectroscopy m m (Lutzgendorf et al., 2011), which is probably affected (k (k ) ) by shot-noise bias. r r ( ( P P σ 10 σ 5 the innermost core regions of high-­ SINFONI KMOS FLAMES SINFONI KMOS FLAMES density systems, thus finally opening up (790) (96) (700) (52) (82) (276) the possibility­ of properly exploring the kine­matics of Galactic globular clusters 0 12 0 123 at sub-arcsecond scales (see Figures 1 log r (arcseconds) log r (arcseconds) and 4). For comparison, note that no proper motions have been determined in of the red giant branch with good signal- knowledge of the visible matter density the innermost 10 arcseconds of these to-noise in reasonable exposure times, distribution and the kinematic profiles dense globular clusters. For example, in the horizontal branch level is always can provide reliable estimates of the the case of NGC 6388, proper motions brighter than I = 16.5 (i.e., all the targets stellar densities, mass-to-light ratios, have been measured at only r > 20 arcsec- are located at distances < 16 kpc). More- and total cluster masses. onds (Watkins et al., 2015). over, we included only globular clusters 3. The exploration of the kinematics in with [Fe/H] > –1.8, showing metallic lines the proximity of the cluster tidal radius, Figure 5 summarises the results obtained deep enough to guarantee a few km s–1 which has major implications for the from the analysis of 6275 stars sampling accuracy in the radial velocities measure- understanding of the physical origin of the entire radial extension of 11 Galactic ments obtained from low-resolution recently claimed “extra-tidal structures”, globular clusters (Ferraro et al., 2018). This spectra. the interplay with the external tidal dataset allowed us to accurately deter- field, as well as the possible presence mine the systemic velocity and velocity As a first step, the MIKiS survey is of small dark matter halos or modifica- dispersion profile of each system, as well expected to provide the full characteri­ tions to the theory of gravity. as to investigate the presence of ordered sation of the line-of-sight internal kine- 4. A detailed characterisation of the kine- motions. It also provides the first kine- matics of each target cluster, from the matics of multiple populations with matical information for two poorly investi- innermost to the outermost regions. ­different light-element content, to gated clusters: NGC 1261 and NGC 6496. Once combined with measurements of ­provide crucial constraints to globular In the majority of the surveyed systems proper motion, the global project will cluster formation scenarios. we find evidence of rotation within a few ­provide the full 3D view of the velocity half-mass radii from the centre. These space of each system, obtained from results are in overall agreement with the hundreds individual stars, with crucial MIKiS first results predictions of recent theoretical studies, impact on many hot topics of globular suggesting that the detected signals cluster science. In particular, the MIKiS The results obtained so far clearly could be the relics of significant internal survey will provide: demonstrate the revolutionary potential rotation that was set at the epoch of the 1. The very first sub-arcsecond kinematic of the approach adopted in the MIKiS cluster’s formation. This evidence, com- exploration of Galactic globular cluster survey to study the kinematics of colli- bined with other recent results in the cores, thus allowing a systematic search sional systems. In this section, we give ­literature (see for example, Kamann et for signatures of systemic rotation an overview of the first set of results. We al., 2018), suggests that the vast majority 3 4 and intermediate-mass (10 –10 M⊙ ) find that the AO-corrected SINFONI of Galactic globular clusters (if not all of black holes, providing crucial new observations attained an angular resolu- them) display some level of internal rota- insights into the physics and formation tion comparable with that of the HST, thus tion. This might be the remnant signal of processes of both globular clusters allowing us to extract individual spectra a much larger amount of ordered motion and these elusive dark compact for 700 resolved stars within 10 arcsec- imprinted at birth (at the end of the initial objects. onds from the centre of NGC 2808 (see violent relaxation phase) which gradually 2. The determination of the mass distri- Figure 1), and even 52 individual star dissipated via two-body relaxation (see bution and the global amount of spectra within the central 2 arcseconds Tiongco et al., 2017). mass in dark remnants (white dwarfs, of the high-­density cluster NGC 6388 (see neutron stars, stellar mass black Lanzoni et al., 2013). This is indeed an Figure 6 shows the unprecedented rota- holes), since the kinematic profiles are unprecedented achievement; for the very tion curve derived for M5 (Lanzoni et al., sensitive to the whole mass enclosed first time, the radial velocities of hundreds 2018a). The velocity dispersion profile within stellar orbits. The simultaneous of individual stars have been measured in and the rotation curve in this cluster were

The Messenger 172 – June 2018 21 Astronomical Science Ferraro F. R. et al., MIKiS

Figure 5. Projected velocity dispersion profiles for 11 Galactic globular clusters observed in the MIKiS 4 survey (red filled circles). The solid lines correspond to the projected velocity dispersion profiles of the King models that best fit the observed density/­ 3 surface brightness distributions (from Ferraro et al., 2018). 2

1 NGC 288 NGC 6496 NGC 6171 determined from the radial velocity of more than 800 individual stars observed out to 700 arcseconds (~ 5 half-mass 5 radii) from the centre. The rotation curve 4 obtained is the cleanest and most coher- ent pattern ever observed in a globular 3 ) –1

cluster. The rotation axis has been s 2 NGC 3201 NGC 6723 NGC 1261

­measured in distinct concentric annuli at m (k

different distances from the cluster centre ) r ( and it turns out to be strikingly stable P (having a constant position angle of 145 σ 6 degrees with respect to the north-south direction at all surveyed radii). The well- 4 defined shape of the rotation curve is fully consistent with cylindrical rotation. The 2 NGC 1904 NGC 6254 NGC 5927 star density distribution shows a clear 10 flattening in the direction perpendicular to 10 1001000 the rotation axis, with the ellipticity (e) 8 increasing with increasing distance from the cluster centre, reaching a maximum 6 of e ~ 0.14 at r > 80 arcseconds. The peak 4 of the projected rotation velocity curve NGC 5272 NGC 362 (~ 3 km s−1) has been found at ~ 0.6 half- 2 mass radii, and its ratio with respect to 10 1001000 10 1001000 the central velocity dispersion is Vpeak /σ0 r (arcseconds) ~ 0.4. All of these results suggest that M5 is an oblate rotator that is seen almost edge on. Figure 6. The unprece- 4 dented rotation curve M5 obtained for M5 (­Lanzoni Figure 7 shows the results obtained in et al., 2018a). The blue another intriguing cluster: NGC 5986 2 circles mark the mean )

(Lanzoni et al., 2018b). The velocity dis- –1 stellar velocity as a s function of the projected persion profile (left panel) indicates a m

(k distance on either sides ­significant deviation from the King model 0 of the rotation axis (XR). R)

in the outer region (r > 100 arcseconds) (X The red line represents

t

ro the cylindrical rotation of the system. The clear-cut evidence V of systemic rotation is even more impres- –2 curve, which well repro- duces the observed sive. Indeed, the observed rotation curve profile. (right panel of Figure 7) is one of the best examples of solid-body rotation ever –4 found in a globular cluster. This is the first –400 –200 04200 00 time that these two kinematic features XR (arcseconds) have been jointly observed in a Galactic star cluster, and such co-existence in the physical interpretation of the struc- ubiquity of detections of even modest makes the case of NGC 5986 particularly ture and kinematics of the peripheries of signatures of rotation in globular clusters intriguing. In fact, these features may globular clusters and their possible role indicates that most of these systems­ result from the evolutionary interplay as new tools for near-field cosmology. were born with significant amounts of between the internal angular momentum ordered motion, thus pro­viding significant of the system and the effect of the tidal The first results of the MIKiS survey have constraints on globular cluster formation field of the host galaxy (Tiongco et al., highlighted the importance of an appro- models. On the other hand, the detection 2016, 2017). Such a discovery is particu- priate search for rotation signals over of intriguing features, such as those larly timely, in light of the growing interest the entire cluster extension. In fact, the observed in NGC 5986, sheds new light

22 The Messenger 172 – June 2018 4

8 2

)

1

–

s

m

(k 0

R)

(X

t

ro

V

) –2 –1

s 6 m (k ) r (

P – 4 σ –2 00 0 200 XR (arcseconds)

4 Figure 7. Left panel: Velocity dispersion profile of NGC 5986, showing a clear increasing trend in the outskirts. Right panel: Rotation curve of NGC 5986. The blue circles mark the mean stellar­ velocity as a function of the projected distance on either side of the rotation axis (XR). The solid line is the best least- squares fit to the observed points (from Lanzoni et 1.522.5 al., 2018b). log r (arcseconds)

on the complex interplay between globular­ Ferraro, F. R. et al. 2018, ApJ, 860, 50 Tiongco, M. A. et al. 2018, MNRAS, 475, L86 cluster internal evolution and the tidal Harris, W. E. 1996, AJ, 112, 1487 Watkins, L. L. et al. 2015, ApJ, 803, 29 Kamann, S. et al. 2018, MNRAS, 473, 5591 field of the Galaxy. King, I. R. 1966, AJ, 71, 64 Lane, R. R. et al. 2010, MNRAS, 406, 2732 Notes Lanzoni, B. et al. 2013, ApJ, 769, 107 References Lanzoni, B. et al. 2018a, ApJ, in press, a The shape of the profile is fixed by the concentration arXiv:1804.10509 parameter c, defined asc = log(rt /rc), where rc is Bellini, A. et al. 2014, ApJ, 797, 115 Lanzoni, B. et al. 2018b, ApJ, submitted the core radius of the model (roughly correspond- Carballo-Bello, J. A. et al. 2012, MNRAS, 419, 14 Lapenna, E. et al. 2015, ApJ, 798, 23 ing to the cluster-centric distance at which the Carretta, E. et al. 2009, A&A, 505, 117 Lutzgendorf, N. et al. 2011, A&A, 533, A36 ­projected density of stars drops to half of its central Chen, C. W. & Chen, W. P. 2010, ApJ, 721, 1790 Piotto, G. et al. 2015, AJ, 149, 91 value), and rc is the tidal radius (at which the stellar Dubath, P. et al. 1997, A&A, 324, 505 Tiongco, M. A. et al. 2016, MNRAS, 461, 402 density becomes zero). Tiongco, M. A. et al. 2017, MNRAS, 469, 683 )/ESO atacamaphoto.com G. Hüdepohl (

A drone’s eye view of the VLT.

The Messenger 172 – June 2018 23 Astronomical Science DOI: 10.18727/0722-6691/5077

Constraining Convection in Evolved Stars with the VLTI

Claudia Paladini 1 between stellar parameters and con- 2013). At this stage the need for high Fabien Baron 2 vective sizes, which are determined on angular resolution images became clear. Alain Jorissen 3 the basis of three-dimensional stellar Jean-Baptiste Le Bouquin 4 convection models. Our results open Bernd Freytag 5 up a new era for the characterisation Stellar surfaces with PIONIER Sophie Van Eck 3 of stellar convection in stars other than Markus Wittkowski 1 the Sun. The PIONIER instrument (Le Bouquin et Josef Hron 6 al., 2009) combines the light of four tele- Andrea Chiavassa 7 scopes (the four Auxiliary Telescopes, or Jean-Philippe Berger 4 The surface of the Sun is populated by the four Unit Telescopes) in the H-band. Christos Siopis 3 about two million convective cells that PIONIER is very stable and efficient, and Andreas Mayer 6 are roughly 2000 km in size. According is best suited to imaging bright targets Gilles Sadowski 3 to the theory outlined by Schwarzschild (see for example, Wittkowski et al., 2017). Kateryna Kravchenko 3 (1975), when the Sun evolves towards Shreeya Shetye 3 the red giant branch, its atmosphere will The semi-regular variable π1 Gruis, an Franz Kerschbaum 6 inflate and, because of the lower surface evolved star with a period of 195 days Jacques Kluska 8 gravity, only a few convective cells will and a parallax of 6.13 ± 0.76 milliarcsec- Sofia Ramstedt 5 survive at the surface. On the other hand, onds, was observed with PIONIER in it is known that stars evolving along the September 2014 (Figure 1). Given the giant branch lose mass via stellar winds. complexity of the target, we collected 1 ESO Mass loss from evolved stars is one of as many uv points as possible, which 2 Department of Physics and Astronomy, the crucial­ processes for galactic chemis- resulted in a total of two nights of obser- Georgia State University, USA try. Stellar convection is one of the vations. The data were obtained using 3 Institut d’Astronomie et d’Astrophysique, dynamical processes that plays a crucial the compact and the medium arrays of Université libre de Bruxelles, Belgium role in shaping the inner atmospheres the VLTI, which are best suited to imaging 4 Université Grenoble Alpes, CNRS, of evolved stars. In particular, through its targets with a diameter of about 20 milli- IPAG, France interplay with dust formation, it contrib- arcseconds, as in the case of π1 Gruis. 5 Department of Physics and Astronomy, utes to the mass-loss process. The switch between the array configura- Uppsala University, Sweden tions was done within one week to mini- 6 Department of Astrophysics, University The angular resolution of optical interfer- mise the effect of variability of the star. of Vienna, Austria ometry allows the stellar discs of evolved The H-band (like the K-band) gives access 7 Université Côte d’Azur, Observatoire de stars to be resolved, as well as smaller to the photospheres of evolved stars. la Côte d’Azur, CNRS, Lagrange, Nice, structures such as convective granulation. AGB stars with oxygen-rich chemistry, France However, for several years we have been such as π1 Gruis, are ideal candidates for 8 Institute of Astronomy, KU Leuven, limited by the number of available aper- studies of the stellar surface convection, Belgium tures. Several papers have reported as oxygen-rich dust is transparent at asymmetric structures in evolved giants. those wavelengths. The departure from spherical symmetry We used the Precision Integrated-Optics was measured either by comparing We collected 303 spectrally dispersed Near-infrared Imaging ExpeRiment ­visibilities observed at different position visibilities (three spectral channels at (PIONIER) at the Very Large Telescope angles, or via measurements of closure 1.625, 1.678, and 1.730 micrometers) and Interferometer (VLTI) to image the stellar phase different from zero or ±180 degrees. 201 closure phases. Model-independent surface of the S-type Asymptotic Giant The observations were then interpreted images have been reconstructed for Branch (AGB) star π1 Gruis. The angular by superimposing bright spots with vary- each spectral channel using the software resolution of two milliarcseconds allowed ing contrasts on limb-darkened discs packages SQUEEZE (Baron et al., 2010), us to observe the surface of this giant (Young et al., 2000; Ragland et al., 2006; and the Multi-aperture image Reconstruc- star in unprecedented detail. At the Montarges et al., 2016, 2017). In other tion Algorithm (MiRA, Thiebaut, 2008). observed wavelength the stellar disc cases, the interpretation was done using Figure 2 shows the result of the recon- appears circular and dust-free. More­ physical models including radiative trans- struction algorithms, which use different­ over, the disc is characterised by a few fer (for example Cruzalebes et al., 2013, principles but give two very robust and bubbles of a convective nature. We Arroyo-Torres et al., 2015). However, similar results in this case. The stellar determine the contrast, and the charac- because of the scarce uv coverage, the disc is nearly round, populated by several teristic horizontal length-scale of the interpretation of the data was highly non- patterns of a convective nature. convective granules. The latter is deter- unique, and asymmetric structures could mined, for the first time, directly from also be interpreted as indications of the the image, without involving the usual presence of a binary companion (Mayer Characterising stellar convection geometric modelling that has been used et al., 2014), or even an increase of the in the literature. The measurements density scale-height in the equatorial The three quantities characterising con- fall along empirical scaling relations plane due to rotation (van Belle et al., vective granules are the contrast, the size

24 The Messenger 172 – June 2018 ­ Paladini C. C. ESO & B. Lazareff (LAOG)

Figure 1. (Above) Left: λcentre = 1.625 µm λcentre = 1.678 µm λcentre = 1.730 µm the PIONIER instrument 1.0 in the VLTI Lab. Right: a) b) c) the four Auxiliary Tele- 10 10 10 0.8

scopes in the compact ) ) ) Paladini et al. 2018

configuration. as 5 as 5 as 5

(m (m (m 0.6

ion 0 ion 0 ion 0 0.4 –5 –5 –5 Declin at Declin at Declin at 0.2 –10 –10 –10

0.0 –10–50 510 –10–50 510 –10–50 510 Right ascension (mas) Right ascension (mas) Right ascension (mas)

1.0 aಿ) bಿ) cಿ) 10 10 10 0.8

Figure 2. (Right) Upper ) ) )

panels: the three images as 5 as 5 as 5

in different spectral (m (m (m 0.6 channels of the surface ion 0 ion 0 ion 0 of π1 Gruis reconstructed with SQUEEZE. The 0.4 white circle in the upper –5 –5 –5 Declin at Declin at Declin at left panel represents 0.2 the angular resolution of –10 –10 –10 the observations. Lower panels: same as above, 0.0 using the image recon- –10–50 510 –10–50 510 –10–50 510 struction algorithm MiRa. Right ascension (mas) Right ascension (mas) Right ascension (mas)

of the granules, and their characteristic derived the power spectrum density of that best fits the spectral energy distri­ lifetime. The last of these cannot be the image; this method is commonly used bution; 2) a Gaussian profile; and 3) determined as we currently only have in several fields of astronomy, especially a square mask that excludes the steep observations obtained at one epoch. when modelling stellar con­vection. How- decrease in brightness of the limb The contrast was obtained for every ever, a mere power spectrum of our ­darkening in the image. ­individual spectral channel after correct- image would simply provide the diameter ing the image for limb darkening. We of the star. As we are interested in the After subtracting the limb darkening, obtained a contrast between 12% and characteristic size of granulation, we sub- we scaled the background of the image 13%, with a slight increase towards short tracted the stellar disc from the image using the average over the image, and wavelengths where the contamination using dedicated masks. Three masks then added space around the image to from molecular opacities becomes more were designed: 1) a limb darkening profile better isolate the maximum power scale. ­significant. To derive the characteristic obtained from the Model Atmospheres The resulting power spectrum density is scales of the granules in the images, we in Radiative and Convective Scheme shown in Figure 3. The maximum power did not use any geometric model, but (MARCS) model (Van Eck et al., 2017) corresponds to a typical granulation size

The Messenger 172 – June 2018 25 Astronomical News Paladini C. et al., Constraining Convection in Evolved Stars with the VLTI

MiRa of the order of 5.3 (±0.5) milliarcseconds –2.5 –2.5 (mas), which corresponds to a linear 1.625 µm SQUEEZE 1.678 µm MiRa size of 1.2 (± 0.2) × 1011 m at the distance ) ) r] –3.0 1.730 µm r] –3.0 of π1 Gruis. Paladini et al. 2018 owe owe

p –3.5 p –3.5 ξ ξ

–4.0 Granulation size across the Hertzprung– QRT[ QRT[ –4.0 Russell diagram g (S g (S

lo –4.5 lo –4.5 The predictions from a three-dimensional –5.0 –5.0 model including convection for AGB stars –2.5 –2.0 –1.5 –1.0 –0.5 0.0 0.5–2.5 –2.0 –1.5 –1.0 –0.5 0.00.5 are still at an exploratory stage. The log (ξ [cycles mas–1]) log (ξ [cycles mas–1]) model grids available in the literature can reproduce solar observations. However, Figure 3. (Left) The power spectrum density of the of the box, while the area on the right is the angular they cover a different stellar parameter three spectral channels of the SQUEEZE images. resolution of the observations. (Right) The power The peaks of the three curves have been averaged spectrum density obtained for the first spectral space from that of our star (Freytag et al., after smoothing to derive the power carrying length. channel and the two different image reconstruction 1997; Tremblay et al., 2013; Trampedach The grey shaded area on the left represents the size algorithms. et al., 2013). Under the assumption that stellar convection works in the same way across the Hertzsprung–Russell diagram, 14 Figure 4. The characteristic we extrapolated our results and com- ­granulation size of convection derived from the π1 Gruis pared the granulation size determined so ­PIONIER images (triangle), 12 log g = –0.4 far with model prescriptions relating the ­compared with theoretical characteristic scale to stellar parameters. Paladini et al. 2018 ­predictions extrapolated from the Figure 4 shows that our result, repre- Sun. ) 10 sented by the triangle, is well reproduced (m g by the model prescriptions. x g

lo 8

Outlook log g = 4.4 6 Trampedach The next step of this work will be to add Tremblay the vertical scale information by using Freytag 4 the high spectral resolution mode of the 3.9 3.83.7 3.63.5 3.4 VLTI/GRAVITY instrument (Eisenhauer log Teff (K) et al., 2011). The characteristic lifetime of convection should involve a monitoring Observations of convective granules for Austrian Science Fund (FWF) under project programme that acquires at least an stars less evolved than π1 Gruis would AP23006-N16. We thank all the ESO/VLTI staff for supporting our observations. image per month. require higher angular resolution than the one currently available. The latter could A deeper understanding of convection, be achieved either with longer baselines, References and how this process depends on stellar or moving to shorter wavelengths. Arroyo-Torres, B. et al. 2015, A&A, 575, A50 parameters, will require extending such Baron, F. et al. 2010, SPIE, 7734, 77342I studies to several other targets. An imag- Cruzalebes, P. et al. 2015, A&A, 446, 3277 ing survey of AGB stars will be rather Acknowledgements Eisenhauer, F. et al. 2011, The Messenger, 143, 16 straightforward as the VLTI reaches the Freytag, B. et al. 1997, Science with the VLT Claudia Paladini acknowledges the support of the Interferometer , in Proceedings of the ESO work- right angular resolution to resolve the Fonds National de la Recherche Scientifique (F.R.S.- shop, (Berlin, New York: Springer), 316 convective granules on the surface of FNRS), Belgium. Christos Siopis and Gilles Sadowski Haubois, X. et al. 2009, A&A, 508, 923 such stars. Given the interplay of convec- are supported by the PRODEX office, Belgium. This Le Bouquin, J.-B. et al. 2011, A&A, 535, A67 tion with pulsation and dust formation, research has been funded by the Belgian Science Mayer, A. et al. 2014, A&A, 570, A113 Policy Office under contract BR/143/A2/STARLAB Montarges, M. et al. 2016, A&A, 588, A130 the optimum strategy for future follow up (Shreeya Shetye, Alain Jorissen, Sophie Van Eck). Montarges, M. et al. 2017, A&A, 605, 108 observations would be to use all of the Katheryna Kravchenko is supported­ by a FRIA grant Paladini, C. et al. 2018, Nature, 533, 310 various wavelength bands available at (Belgium). Fabien Baron acknowledges funding by Ragland, S. et al. 2006, ApJ, 652, 650 the VLTI — from H- to N-bands, using the National Science Foundation, NSF-AST numbers Schwarzschild, M. 1975, ApJ, 195, 137 1445935 and 1616483. Jaques Kluska acknowl- Thiébaut, É. 2008, SPIE, 7013, 70131I PIONIER, GRAVITY, and the Multi AperTure edges the Philip Leverhulme Prize (PLP-2013-110). Tremblay, P.-E. et al. 2013, A&A, 557, A7 mid-­Infrared SpectroScopic Experiment Sophie Van Eck thanks the Fondation ULB for its Trampedach, R. et al. 2013, AJ, 769, A18 (MATISSE) — as simultaneously as possi- support. The research leading to these results has Van Eck, S. et al. 2017, A&A, 601, A10 ble so all the ­spatial scales could be cap- received funding from the European Union’s Horizon Wittkowski, M. et al. 2017, A&A, 601, 3 2020 research and innovation programme under Young, J. S. et al. 2000, MNRAS, 315, 635 tured at the same time. Grant Agreement 730890 (OPTICON) and from the van Belle, G. T. et al. 2013, ApJ, 775, 45

26 The Messenger 172 – June 2018 Astronomical Science DOI: 10.18727/0722-6691/5078

A Planet with a Disc? A Surprising Detection in Polarised Light with VLT/SPHERE

Christian Ginski 1, 2 With the Spectro-Polarimetric High- The SPHERE instrument (Beuzit et al., Rob van Holstein 1 contrast Exoplanet REsearch (SPHERE) 2008) is perfectly suited to this task. Attila Juhász 3 instrument at ESO’s Very Large Tele- Recently van Holstein et al. (2017) were Myriam Benisty 4, 5 scope (VLT) we can study the linear able to constrain the polarisation degree Tobias Schmidt 6 polarisation of directly detected planets of the planets around HR 8799 to be lower Gaël Chauvin 4, 5 and brown dwarfs, to learn about their than 1% and the companion to PZ Tel Jos de Boer 1 atmospheres and immediate environ- to be lower than 0.1% with measurements Mike Wilby 1 ments. We summarise here the recent performed with the SPHERE Infra-Red Carlo F. Manara 7 discovery of a low-mass companion in Dual Imaging and Spectrograph (IRDIS). Philippe Delorme 4 polarised light by Ginski et al. (2018). Here, we highlight another recent result: Francois Ménard 4 The object shows an extreme degree of the first detection of a new substellar Gabriela Muro-Arena 2 polarisation, indicating the presence of companion to a young nearby star in Paola Pinilla 8 a circumplanetary disc. polarised light. Til Birnstiel 9 Mario Flock 10 Christoph Keller 1 High-resolution polarimetry of Observations of the CS Cha system Matthew Kenworthy 1 substellar companions Julien Milli 7 The CS Cha system contains a spectro- Johan Olofsson 11, 12 In the past 15 years, numerous substellar- scopic binary, both components of Laura Pérez 13 mass companions to young nearby stars which appear to be solar-type pre-main- Frans Snik 1 have been discovered with high-contrast sequence stars (called T Tauri stars). Nikolaus Vogt 11 and high-angular-resolution imaging. The system is located in the nearby Using resolved photometry and spectros- ­Chamaeleon I molecular cloud at a dis- copy we can study the atmospheres of tance of 165 pc and was previously 1 Sterrewacht Leiden, the Netherlands these objects, which range from plane- ­studied by means of unresolved photo- 2 Anton Pannekoek Institute for Astron- tary to brown dwarf masses. This makes metric measurements, which revealed a omy, University of Amsterdam, the them especially interesting targets to test large infrared excess. This suggests Netherlands planet formation theories. At the same the presence of a circumstellar disc (see, 3 Institute of Astronomy, University of time, the formation of these objects at a for example, Espaillat et al., 2007). The Cambridge, UK few tens or hundreds of astronomical observed spectral energy distribution 4 Université de Grenoble Alpes, CNRS, units is particularly challenging, given the shows a dip at 10 microns, which hints at IPAG, France limited spatial extent and lifetime of circum- the presence of a large cavity in the disc, 5 Unidad Mixta Internacional Franco-­ stellar discs. a possible sign of ongoing evolution. Chilena de Astronomía, CNRS/INSU UMI 3386 and Departamento de High-spatial-resolution polarimetry is a On 18 February 2017 we used SPHERE/ Astronomía, Santiago, Chile powerful tool that can provide a plethora IRDIS to observe the CS Cha system 6 LESIA, Observatoire de Paris, PSL of information about these companions. in near-infrared polarised light with the Research University, CNRS, Sorbonne While the thermal emission of substellar aim of resolving its surrounding disc for Universités, UPMC Université Paris 06, objects is not usually intrinsically polar- the first time. Our observation resolved Université Paris Diderot, Sorbonne ised, scattering by patchy clouds or a ­circumbinary disc with a diameter of Paris Cité, France atmospheric haze can introduce an over- ~ 110 astronomical units (au). We show 7 ESO all linear polarisation. Rotational flattening, this disc in Figure 1a. 8 Department of Astronomy, Steward the presence of orbiting moons, magnetic Observatory, The University of Arizona, fields, or circumplanetary discs can also However, the disc was not the only Tucson, USA cause polarisation. By measuring the detection made that night. We noticed 9 University Observatory Munich, degree and angle of linear polarisation that a faint companion candidate was Faculty of Physics, Ludwig-Maximilians- with high accuracy we can distinguish ­visible at approximately 1.3 arcseconds University, Munich, Germany between these effects and extract atmos- to the west of the primary stars. Remark- 10 Max-Planck-Institut für Astronomie, pheric parameters as well as information ably, this companion is not only visible Heidelberg, Germany about the circumplanetary environment. in intensity (see Figure 1c), but also in 11 Instituto de Física y Astronomía, polarised light (see Figure 1a). It is ­Universidad de Valparaíso, Chile Polarisation has been measured in the extremely faint, with an apparent magni- 12 Núcleo Milenio Formación Planetaria – past for field brown dwarfs, but only tude of 19.2 magnitudes in the J-band. NPF, Universidad de Valparaíso, Chile the latest generation of extreme adaptive-­ Such flux levels are predicted by planetary 13 Departamento de Astronomía, optics imagers at large aperture tele- atmosphere models for objects with a ­Universidad de Chile, Santiago, Chile scopes are allowing us now to open the few times the mass of Jupiter. A particu- parameter space to detect these interest- larly intriguing property of this companion ing low-mass companions to nearby is its high level of polarisation. In our stars. J-band data we measured a degree of

The Messenger 172 – June 2018 27 Astronomical Science Ginski C. et al., A Surprising Detection in Polarised Light with VLT/SPHERE

linear polarisation of ~ 14%. This value Figure 1. Observations was later confirmed with a follow-up 0.5 a) SPHERE/Polarised light of the CS Cha system at multiple wavelengths SPHERE/IRDIS observation in the H-band. and with various instru- ments. The companion To prove that the companion is associ- 0.0 is always marked by a ated with the CS Cha system one needs dashed circle. (a) SPHERE polarised to measure the common proper motion light image. The com- using archival data. CS Cha was observed –0.5 02/2017 panion is seen in polar- with the Nasmyth Adaptive Optics System ised light along with the Near-Infrared Imager and Spectrograph disc around the central binary star. The corona- 0.5 b) HST/WFPC2/I-band (NACO, Lenzen et al., 2003) at the VLT in graph that was used is the K-band 11 years prior to our SPHERE indicated by a grey observations. Furthermore, we found hatched circle. I-band observations taken in February (b–e) Total intensity 0.0 unpolarised images of 1998 with the Hubble Space Telescope’s the companion. The Wide Field and Planetary Camera 2 (HST/ stellar PSF was partially WFPC2). Re-reducing these data sets, subtracted to increase 02/1998 we were able to recover the companion –0.5 the companion contrast, also creating the dark- (see Figures 1 b and e). With a 19-year s) bright patterns visible. baseline, we could then show that CS Cha 0.5 c) VLT/SPHERE/J-band The position of the and the companion have nearly the same ­central binary is marked proper motion on the sky (see Figure 2). second with a star symbol.­ rc

The small differential motion that we (a 0.0 found is consistent with the orbital motion

that is expected for a low mass com­ at ion panion. This makes it very likely that this –0.5 02/2017 object is gravitationally bound to CS Cha. Declin Δ

The next step in our analysis was to 0.5 d) VLT/SPHERE/H-band investigate the possible causes for the high degree of polarisation. One possi­ bility could be the presence of a large amount of interstellar dust between the 0.0 Solar System and the CS Cha system. This would be especially likely if CS Cha is located deep within the Chamaeleon I –0.5 06/2017 molecular cloud. We measured the degree of polarisation of the unresolved e) VLT/NACO/K-band primary stars in our J- and H-band 0.5 SPHERE data sets and found that their light was polarised to less than 1%. This strongly suggests that the degree of 0.0 polarisation of the companion is intrinsic and not caused by interstellar dust. –0.5 02/2006 A planet with a disc? –1.0 –0.5 0.00.5 1.01.5 2.0 ΔRight ascension (arcseconds) Since we have multiple observations of the companion in various photometric tude relative to the host star. We then phere models for substellar objects. bands we can attempt a characterisation. use the known brightness of the host to In Figure 3, we show two model spectra, In particular, we are interested in con- translate these relative measurements obtained for an object of 5 Jupiter straining its mass and determining the into absolute fluxes. The SPHEREH -band masses (MJup) and one of 20 MJup. These causes of its high degree of polarisation. photometry has larger uncertainties model spectra include clouds in the because the observations were taken in atmosphere models, but do not include In Figure 3 we show all the available poor weather conditions. circumplanetary material. ­photometric measurements along with upper limits for non-detections. We We compared the companion photometry We found that the J-H colour of the com- always measure the companion magni- to PHOENIX (Helling et al., 2008) atmos- panion is somewhat consistent with a

28 The Messenger 172 – June 2018 272 5-MJup planet. However, the model spec- VLT/SPHERE trum overpredicts the flux in the NACO 270 HST/WFPC2 K- and L-bands and underpredicts it in

) the HST I-band. A 20-M planet, on the 268 if background VLT/NACO Jup

ees other hand, completely overpredicts the

egr 266 flux across all photometric bands. We conclude that no standard atmosphere e (d 264 model could reproduce these peculiar angl photometric measurements. Additionally, 262 clouds in planetary atmospheres are osition 260 not expected to cause linear polarisation if bound of more than a few percent (Stolker et al., 258 2017).

256 The presence of a circumplanetary disc seen at a high inclination, i.e., close to 1.7 edge-on, can produce a high degree of linear polarisation in the companion.

)P Such a strongly inclined disc would then 1.6 also block some of the light from the companion itself. This would naturally seconds

rc explain why “naked” planetary atmos- (a 1.5 phere models are a bad fit to the available photometry. We can put one further con- straint on a potential circumplanetary 1.4

Separation disc. It needs to be small enough that we are not able to resolve it in our SPHERE 1.3 images. This means that its diameter must be less than 4 au. 1995 2000 2005 2010 2015 2020 Time (year) After some first attempts at modelling the Figure 2. (Above) Astro- observations we realised that an inclined CS Cha metric measurements –12 disc alone still does not explain the high 10 AMES-DUSTY 5 M of the companion rela- Jup degree of polarisation. In fact, our models AMES-DUSTY 20 M tive to the unresolved Jup primary stars. The grey underpredict the degree of polarisation CS Cha b/B “wobbled” area is the by a few percent and do not fit the pho- area where background tometry. However, if we include a very objects would be 10 –13 expected, while the area thin dusty halo, then we can nearly repro- H J W W between the dashed duce all of the measurements. This halo B– B– 06 14 lines is where gravita- /B /B

F8 has a dust mass two orders of magnitude s ಿ k /L / tionally bound objects less than that of the disc itself. We show are expected. CO CO HERE HERE the best-fitting models in Figure 4. For 10 –14 ) SP WFPC2/F6 WFPC2/ NA SP NA

–2 simplicity, each model is computed for

/m a single dust grain size only. The models (W

λ with 0.1- and 1.0-micron particle sizes F

λ reproduce the companion photometry 10 –15 well. The smaller grains, on the other Figure 3. (Left) Photo- hand, lead to an overprediction of the metric measurements degree of polarisation, while the larger (circles) and upper limits (triangles) of the com- grains slightly underpredict the polarisa- panion (red symbols) in tion, especially in the J-band. It is thus –16 10 different bands and with reasonable to assume that a more com- different instruments. plex mixture of differently sized grains For comparison we also plot the photometry of should be able to reproduce the meas- the unresolved primary ured polarisation. 10 –17 stars (blue symbols), as well as theoretical Since the flux of the companion is attenu- models for a 5-M and 10 0 101 Jup ated by its surrounding disc, we need a a 20-MJup planet (solid λ (µm) and dashed lines). higher-mass object to fit the photometry

The Messenger 172 – June 2018 29 Astronomical Science Ginski C. et al., A Surprising Detection in Polarised Light with VLT/SPHERE

compared to the “naked” atmosphere 10 –15 Figure 4. (Left) Com- models. In this case we use a 20-M panion photometry and Jup degree of linear polari- planet. sation along with our best fitting models. These first models fit well with the ­Different colours and ­measurements, but they still suffer a line styles denote differ- ent inclinations of the )

degeneracy between the mass of the –2 10 –16 circum-companion disc central object, the inclination of the /m as well as different dust (W ­circumplanetary disc and the dust grain grain sizes. Triangles λ

F show upper limits, while sizes. Therefore we caution that the solu- λ circles are current tion we find is likely not the only one. measurements. However, since the modelled disc inclina- tion of ~ 80° is rather high, we can be 20 MJup /0.1 µm/77° sure that the companion is not signifi- –17 10 20 MJup /1.0 µm/80° cantly more massive than our current 20 MJup /2.0 µm/75° estimates. More massive central objects would require a stronger attenuation to 50 fit the photometry and thus a higher disc inclination.

) 40

We show a schematic of the full CS Cha (% system in Figure 5 as described in our ee model. The elevation of the companion 30 degr along the line of sight is unknown, so we do not know if it is partially illuminated 20

by the central binary, or completely larisation

­shadowed by the circumbinary disc. We Po conducted tests to investigate the possi- 10 bility of additional illumination of the com- panion by the central binary and found that this had only a marginal effect on our 0 Figure 5. (Below) modelling. 0.5 1.03.0 ­Schematic of the λ (µm) CS Cha system. ­Distances and sizes are not to scale. Planet formation in the CS Cha system er pc rv Given what we know about the CS Cha 5 16 ~ system, we can speculate on how the Obse companion may have formed. The circum- stellar disc that we detected in polarised Dusty halo u scattered light only extends out to ~ 55 au. a It is possible that the disc extends further, < 4 but we do not see it in scattered light Disc because it is partially self-shadowed. However, it seems unlikely that the disc extends out to the companion position < 30.6 au at 214 au.

Given the available astrometry, we com- puted possible orbits of the companion. ≥ 214 au We found that orbits that are circular and co-planar with the circumstellar disc do the primary stars. Furthermore, the multiple stellar system. In multiple stellar not fit the available data. We further find ­circumplanetary disc may be misaligned systems such misalignments are quite that the companion’s orbit must be at with both the orbital plane and the stellar common (see, for example, simulations least slightly eccentric if the companion spin axis. Such misalignments would by Bate, 2012). mass is indeed as low as our modelling not be predicted if the companion formed work predicts. The orbital plane is likely in the disc around the primary stars. In the future we will need follow-up misaligned with the plane of the circum- Thus we speculate that the companion observations with the Atacama Large stellar disc and thus with the spin axis of may have formed as a component of a ­Millimeter/submillimeter Array (ALMA),

30 The Messenger 172 – June 2018 to constrain the dust mass around the Acknowledgements (2004–2008), grant number 226604 for FP7 (2009– companion as well as the extent of the 2012) and grant number 312430 for FP7 (2013– Our new observations were performed with SPHERE 2016). Christian Ginski would like to thank Donna gas disc of the stellar spectroscopic at the VLT. SPHERE is an instrument that has been Keeley for language editing of the manuscript. binary. Also, spectral observations in the designed and built by a consortium consisting of near-infrared are needed to better charac- IPAG (Grenoble, France), MPIA (Heidelberg, terise the companion. In particular, we ­Germany), LAM (Marseille, France), LESIA (Paris, References France), Laboratoire Lagrange (Nice, France), INAF– will need (HST/WFC3) observations as Osservatorio di Padova (Italy), Observatoire de Bate, M. R. 2012, MNRAS, 419, 3115 the limitations of current ground-based Genève (Switzerland), ETH Zurich (Switzerland), Beuzit, J.-L. et al. 2008, SPIE, 7014, 18 instruments do not allow us to detect the NOVA (Netherlands), ONERA (France) and ASTRON Espaillat, C. et al. 2007, ApJ, 664, L111 spectrum of the companion. (Netherlands) in collaboration with ESO. SPHERE Ginski, C. et al. 2018, A&A, submitted was funded by ESO, with additional contributions Helling, C. et al. 2008, ApJ, 675, L105 from CNRS (France), MPIA (Germany), INAF (Italy), van Holstein, R. G. et al. 2017, SPIE, 10400, 15 The CS Cha system offers concrete FINES (Switzerland) and NOVA (Netherlands). In Lenzen, R. et al. 2003, SPIE, 4841, 944 ­evidence of a formation pathway for addition, SPHERE received funding from the Euro- Stolker, T. et al. 2017, A&A, 607, 42 wide planetary-mass companions and pean Commission Sixth and Seventh Framework Programmes as part of the Optical Infrared Coordi- shows the power of polarimetry as a tool nation Network for Astronomy (OPTICON) under for planet characterisation. grant number RII3-Ct-2004-001566 for FP6 ESO/H. Avenhaus et al./DARTT-S collaboration al./DARTT-S et Avenhaus ESO/H.

SPHERE image of the enormous dust disc surrounding the T Tauri star IM Lup.

The Messenger 172 – June 2018 31 Astronomical News ESO/P. Horálek ESO/P.

Upper: A planetarium show at the ESO Supernova Lower: ESO and VDL ETG Projects B.V. (the Planetarium & Visitor Centre, which opened its ­Netherlands) sign a contract for the manufacture, doors to the public on Saturday 28 April 2018. assembly, testing and delivery of the Segment Support Mechanics, responsible for holding and controlling the 798 mirror segments of the primary mirror of the Extremely Large Telescope.

32 The Messenger 172 – June 2018 Astronomical News DOI: 10.18727/0722-6691/5079

Report on the ESO Workshop Planning ESO Observations of Future Gravitational Wave Events

held at ESO Headquarters, Garching, Germany, 31 January–1 February 2018

Bruno Leibundgut 1 gamma-ray burst (GRB170817A) two events. The programmatic aspects of Ferdinando Patat 1 ­seconds later, the search for an optical/ ESO observations were also exhaustively infrared counterpart was on. Within a explored.1 few hours, an optical counterpart was 1 ESO detected in the galaxy NGC 4993. Spec- The first session was focused on troscopic follow-up observations began GW170817 observations. The gravita- immediately, resulting in a detailed record tional wave signal was presented Understanding the nature and results of the evolution of the event over the fol- and compared to that from black hole of black hole and neutron star mergers lowing two weeks. mergers by Sarah Antier (Laboratoire de has become a hot topic in astrophysics. l’Accélérateur Linéaire Orsay), followed The combination of gravitational wave ESO and ESA telescopes and instru- by a description of the event as seen and electromagnetic observations of ments participated in this global observ- at optical and near-infrared wavelengths GW170817/GRB 170817A has triggered ing campaign. Parts of the community (Stephen Smartt, Queen’s University new and exciting science projects. The focused on the search of the optical ­Belfast), in X-rays (Maria Grazia Bernardini, timeline for observations of gravitational counterpart with ESO’s Visible and Infra- Laboratoire Univers­ et Particules de wave events lies between seconds and red Survey Telescope for Astronomy Montpellier) and in gamma rays (Roland days, and coordinated observations (VISTA) and the VLT Survey Telescope Diehl, Max Planck Institute for Extrater- of electromagnetic radiation are critical (VST), but as soon as the GRB detected restrial Physics [MPE] in Garching). when probing the nature of these events. by the ESA INTErnational Gamma-Ray The great success of the observations Astrophysics Laboratory (INTEGRAL) Marina Rejkuba (ESO) reported on the of GW170817/GRB 170817A from more ­satellite and its optical counterpart had ESO observations and the activities than 50 observatories has highlighted been identified, the event was followed up ­associated with the release of the data the importance of coordination between using several spectrographs and imagers. to the community. Optical observations different instruments and facilities. This of GW170817 could only be conducted two-day workshop focused on what has for a couple of hours before the object been learned from ESO observations of Workshop goals set each evening in Chile, with several GW170817/GRB 170817A, and discussed instruments being used simultaneously strategies for coordinating observations The goal of the workshop was to bring on the VLT. The ESA satellites INTEGRAL of future events. the community together to discuss the and X-ray Multi-Mirror satellite (XMM- best way to obtain ESO observations of Newton) also participated in the observ- future gravitational wave events. Despite ing campaign, and Peter Kretschmar­ Background the speed with which the workshop was (European Space Agency, ESA) gave organised — it was announced in the an account of the activities required at The first detection of an electromagnetic ESO Science Newsletter on 20 December the operations centres in order to obtain counterpart of a gravitational wave event 2017 — 55 participants had registered these data at short notice. had a historic dimension, as it connected by the deadline in early January. two seemingly separate “universes”. Since it is still very early days for the ­Several mergers of black holes had been The speaker list was partially defined ­electromagnetic observation of gravita- observed prior to that, indicating black through the Principal Investigators (PIs) tional wave events, Anders Jerkstrand holes of several tens of solar masses; this of exisiting proposals. Eight of the 26 (Max Planck Institute for Astrophysics, presented a puzzle, as black holes of speakers were female (corresponding to Garching) gave a theorist’s view of what these sizes had not previously been antici- 31%), which reflected the gender distribu- we should expect and how to make pated. The detection of gravitational tion amongst the registered participants sense of the observations of GW170817. waves — a technical feat requiring meas- (29% female). The first day of the pro- He gave a comprehensive overview of urements of strains of a few times 10–20 gramme was dedicated to assessing the what the signatures of the r-process ele- — in 2015 was epochal, and was recog- status of the gravitational wave detec- ments would look like in the optical and nised with the Nobel Prize in Physics in tions and their follow-up observations, near-infrared spectral sequences, and 2017. While black hole mergers are not in particular for GW170817; while the sec- outlined where we still have significant expected to carry an electromagnetic ond day focused on the planning and gaps in our interpretation of the spectra. ­signal, theoretical modelling predicted that coordination of future observations. Each There remains plenty of room for future the merger of two neutron stars would day finished with an extensive discussion observations to clarify the many questions lead to short gamma-ray bursts (GRBs), session. On 31 January, the past and and uncertainties we still have in respect and would potentially be site of the current ESO observations of (fast) tran- of these events. The session ended with ­formation of heavy elements through sients were discussed, and potential a presentation by Nial Tanvir (University the r-process. ­lessons for future observations debated. of Leicester) on his experience of ESO The afternoon of 1 February was entirely observations of fast transient phenomena, When, on 17 August 2017, an unusal devoted to a community discussion of focusing on gamma-ray bursts. Target gravitational event (GW170817) was the best strategies for future electromag- of Opportunity observations have been observed that coincided with a short netic observations of gravitational wave offered at the VLT since the beginning of

The Messenger 172 – June 2018 33 Astronomical News Leibundgut B. & Patat F., Report on the Workshop “Planning Future GW Observations”

operations, with the addition of refine- The discussion session covered past mean a serious interruption to the ments such as the rapid response mode ESO observations, and aimed to identify uploaded schedule, requiring the corre- about 10 years ago. This frank presenta- what worked and where difficulties were sponding recovery of the schedule time- tion was an excellent basis for a discus- encountered. The panel members were line afterwards. There may also be point- sion on how ESO operations could help ­Stefano Covino, Marina Rejkuba, Steven ing constraints for satellites which need to secure critical data for similar events in Smartt and Nial Tanvir. The open discus- to be evaluated before schedule interrup- the future. sion yielded some interesting comments, tions. Aitor Ibarra (ESA) and Richard and comparisons were made with the ­Saxton (ESA) set out a new tool for the The afternoon session was reserved for experience of using ESO telescopes for improved coordination of observations presentations of ongoing projects dedi- observations of gamma-ray bursts. It and information sharing. cated to the follow-up of transient events. was concluded that overall ESO provided ESO is supporting several such pro- valuable — and sometimes unique — The afternoon was devoted to a discus- grammes, either with its own telescopes resources that can be essential, providing sion centred on the optimal planning of or by hosting dedicated experiments at insights in areas where theoretical predic- future observations, including the best its sites. These include the following tions are lacking. Recommendations possible coordination of ESO telescopes ­projects: the public survey called VIsta were made to strengthen the communi- and instruments. Ferdinando Patat, Enzo Near-infraRed Observations Unveiling cations between various observatories Brocato, Peter Jonker and Erik Kuulkers Gravitational wave Events (VINROUGE), and facilities in order to avoid duplication were the panel members, and a lively which uses VISTA to obtain infrared and to increase synergies. discussion ensued between the panel light curves (Andrew Levan, University and the audience. Several important of Warwick);­ the extended Public ESO The second day of the workshop con- points were raised, among them the wish Spectroscopic Survey of Transient centrated on the planning of future that ESO accept Large Programmes Objects (ePESSTO), which uses the ESO observations. The schedule of science with Target of Opportunity observations. Faint Object Spectrograph and Camera 2 observations with the Laser Interfer­ Additionally ESO was asked to provide (EFOSC2) at the New Technology Tele- ometer Gravitational-wave Observatory rapid delivery of pre-reduced data so that scope (NTT) to ­provide optical spectros- (LIGO)-Virgo collaboration was presented quick assessments and scientific deci- copy (Maria Teresa Botticella, INAF–­ by Marica Branchesi (Gran Sasso Science sions can be made, potentially to then Osservatorio di Capodimonte); the Rapid Institute). The next science run is planned interactively modify observation blocks Eye Mount telescope­ (REM) at La Silla, to start in October 2018 and is scheduled for follow-up observations. ESO will have which is part of a larger collaboration set to last for approximately one year. The to investigate which of these requests up to follow the optical counterparts of principal investigators of the current ESO can be implemented operationally. As a gravitational wave events (Eliana Palazzi, programmes to search for and follow first step, Target of Opportunity Large INAF–IASF Bologna); and the Gamma- up electromagnetic signals from gravita- Programmes were accepted again for Ray burst Optical/Near-infrared Detector tional wave events then presented their ESO Period 102 (from October 2018 to (GROND) instrument on the Max-Planck- plans for the next semester. Elena Pian March 2019). An important discussion Gesellschaft/ESO 2.2-metre telescope (INAF–IASF Bologna) and Paolo D’Avanzo point was whether the (European) com- at La Silla, which obtains photometry in (INAF–Osservatorio Astronomico di Brera) munity could agree to submitting a single seven filters simultaneously (Janet Chen, presented their VLT proposals. A proposal ESO proposal for observations of future MPE Garching). to obtain spectropolarimetry of such gravitational wave events. As a result of events was detailed by Stefano Covino this discussion one single Period 102 A new project that is just starting opera- (INAF–Osservatorio Astronomico di proposal was submitted before the dead- tions is the Gravitational-wave Optical Brera). Aniello Grado (INAF–Osservatorio line of 28 March 2018. ESO was also Transient Observer (GOTO), which was Capodimonte) then presented two ongo- invited to attend the LIGO–Virgo town hall described by Danny Steeghs (University ing programmes with the VST. meeting in April 2018 in Amsterdam, of Warwick). In addition, the long-running where these discussions will continue. Télescopes à Action Rapide pour les A special session on the observing Objets Transitoires (TAROT) project was opportunities with ESA satellites followed. presented by Michel Boer (Centre National The capabilities of INTEGRAL, and in Acknowledgements de la Recherche Scientifique, CNRS). particular its operational constraints, We thank Svea Teupke for providing logistical sup- Future facilities to detect and characterise were introduced by Erik Kuulkers (ESA), port at very short notice. We would also like to thank the electromagnetic counterparts of followed by a presentation on XMM-­ all of the speakers for providing the slides ahead ­gravitational wave events are: BlackGEM, Newton by Norbert Schartel (ESA). Jan- of their presentations so that a seeing-impaired to be installed at La Silla (Paul Groot, Uni- Uwe Ness (ESA) described some pro- ­colleague could follow them on his own laptop. versity of Nijmegen); the Son Of X-Shooter grammatic aspects of the planning and (SOXS), to be installed on the NTT in 2020 coor­dination of space-based observa- Links (Sergio Campana, INAF–Osservatorio tions. The INTEGRAL and XMM-Newton 1 Astronomico di Brera); and the Zwicky schedules are built well in advance of Workshop programme: http://www.eso.org/sci/ meetings/2018/gw2018.html Transient Facility in California (Ulrich he observations and the rapid observa- Feindt, Oskar Klein Centre Stockholm). tion of an unexpected transient may

34 The Messenger 172 – June 2018 Astronomical News DOI: 10.18727/0722-6691/5080

Report on the ESO Workshop Imaging of Stellar Surfaces

held at ESO Headquarters, Garching, Germany, 5–9 March 2018

Markus Wittkowski 1 Liz Humphreys 1

1 ESO

There have recently been tremendous advances in observational techniques enabling the resolution of the surfaces of stars other than the Sun. Current VLTI instruments, SPHERE on the VLT, and ALMA, as well as other interfero- metric facilities, have recently succeeded in resolving stellar surfaces. The work- shop aimed to bring together observers specialising in different techniques and wavelength regimes, and theoreticians working on stellar atmospheres and stellar structure. We aimed to organise a focused workshop with ample time devoted to the discussion of recent Figure 1. Conference photo. The workshop programme was com- images of stellar surfaces and their ex­­ posed of five sessions: tended atmospheres out to a few stellar Multi-BEam combineR (AMBER) and the 1. The Sun as a star; radii, as well as observational strategies Precision Integrated Optics Near-infrared 2. From the Sun towards evolved stars; and the relevant underlying physical Imaging ExpeRiment (PIONIER), have 3. Imaging results; processes. The workshop was the first already demonstrated their capability to 4. Image reconstruction techniques; to be held in the seminar room of the resolve stellar surfaces, while the second- 5. Prospects. new ESO Supernova Planetarium & generation VLTI instruments including the ­Visitor Centre, and it was also the first AO-assisted two-object multi-beam com- Claudia Paladini, Wouter Vlemmings, and workshop for which the new code of biner GRAVITY and the Multi AperTure Alain Chelli led topical discussions on the conduct for ESO workshops & confer- mid-Infrared SpectroScopic Experiment approaches and challenges to imaging ences was in place. (MATISSE) are coming into operation. techniques, the coordination of optical and radio programmes, and observa- The VLT instrument Spectro-Polarimetric tional strategies for imaging, respectively. Until very recently, all of our information High-contrast Exoplanet REsearch instru- Discussion sessions on individual objects about the mechanisms affecting the stel- ment (SPHERE) is also resolving the were also held. Andrea Dupree, Lynn lar surface came either from indirect ­surfaces of the some of the largest stars. Matthews and Christian Hummel led the observations or from studies of the Sun. At the same time, ALMA observations discussions on Betelgeuse, Mira and Vega The stellar surface is the locus that inter- using long baselines have succeeded in respectively. These discussion sessions faces the mechanisms taking place in the resolving stellar surfaces at millimetre led to a new collaboration to study stellar interior (such as convection and wavelengths. A number of other interfer- ­Betelgeuse using multiple facilities quasi- magnetic fields) and diffusion processes ometers at optical and radio wavelengths simultaneously. We enjoyed the confer- which can produce abundance anoma- have also successfully resolved stellar ence venue in the seminar room of the lies. Studying stellar surfaces is important surfaces, including the Center for High new ESO Supernova Planetarium and for advancing our understanding of these Angular Resolution Astronomy (CHARA), Visitor Centre, which we could use for the key physical processes. the Karl G. Jansky Very Large Array first time as a test run. We also had a (VLA), and the Multi-Element Radio Linked nice time with two shows in the new There have recently been an increasing Interferometer Network e-MERLIN. Stellar ESO planetarium that were presented by number of developments in the different atmosphere models have also been the ESO Supernova coordinator, Tania observational techniques that enable advancing over a similar time frame, from Johnston. us to resolve the surfaces of stars other 1D to 3D models that now include the than the Sun. The Very Large Telescope effects of convection. The connection Interferometer (VLTI) is transitioning from between observations and theoretical The Sun as a star its first-generation instruments, which stellar atmosphere models is important focused on spectro-interferometry, to to constrain models and advance our The “Sun as a star” session opened with second-generation instruments, which understanding of physical processes such an invited talk by Sami Solanki, introduc- focus on spectro-imaging and astrometry. as pulsation, convection, and chromo- ing the main physical processes acting in The VLTI instruments, the Astronomical spheric activity. the solar photosphere and the structures

The Messenger 172 – June 2018 35 Astronomical News Wittkowski M. & Humphreys L., Report on the Workshop “Imaging of Stellar Surfaces”

Figure 2. ALMA images of sunspots in the solar chromosphere at 1.25 and 3 millimetres. ALMA (ESO/NAOJ/NRAO)

and dynamics that they produce. Sven supergiant stars. She described how these dynamical processes. Kateryna Wedemayer then outlined what can be spatially resolved spectra reveal complex Kravchenko and Gioia Rau showed learnt from solar observations using ALMA structure in these extended stellar atmos- comparisons between 3D models and in an invited talk (Figure 2). pheres that we do not understand, and observations using both the tomographic which impacts our understanding of method and near-infrared interferometry The radiation observed by ALMA origi- ­stellar activity, magnetic fields, angular with the GRAVITY instrument. Gioia nates mostly from the chromosphere — momentum loss, and stellar cluster Rau also showed modelling of ultraviolet a complex and dynamic layer between populations. spectra that contain chromospheric the photosphere and corona that plays emission lines. a crucial role in the transport of energy Agnes Lèbre (in an invited talk), and the and matter and, ultimately, in the heating next speakers described the techniques of the outer solar atmosphere. The ses- and recent results from spetropolarimetry, Imaging results sion ended with a presentation by Oskar detecting magnetic fields and star spots von der Lühe, in which he described the on the surfaces of Sun-like stars (Emre A major theme of the meeting centred on facilities for the high-angular-resolution Isik, Torsten Böhm) a giant and super- recent imaging results of stellar surfaces imaging of the Sun. Bringing together giant stars (Agnes Lèbre, Arturo López obtained at visible/infrared and radio/­ solar and stellar physicists at this work- Ariste). Susanne Höfner (in an invited talk) millimetre wavelengths, and comparing shop proved to be particularly fruitful. and Bernd Freytag presented the recent them with models and other complemen- Throughout the meeting, discussions fre- status of 3D simulations of convection tary observations. Gail Schaefer started quently revealed the increasing similarities for different types of stars, and in particu- this session by providing an invited over- between these fields. lar, the extension of those simulations view on imaging stellar surfaces with the from solar-type stars to red giant and red CHARA array. This included imaging supergiant stars. gravity darkening on rapid rotators, star From the Sun towards evolved stars spots on magnetically active stars, con- Basic physical considerations and vective cells on red supergiants, winds The workshop programme continued to detailed numerical simulations predict from massive stars, and observations of illustrate the application of physical con- a dramatic increase in the sizes of con- tidal distortions from Roche lobe filling in cepts from the Sun towards evolved stars, vection cells during the late phases of interacting binaries. including processes such as chromo- stellar evolution. The interplay of large spheric activity, surface magnetic fields, and small convection cells, waves, pulsa- In an invited talk, Rachael Roettenbacher pulsation and convection. In an invited tions, and shocks can give the surface concentrated on active giants, which talk, Andrea Dupree highlighted the of an AGB star an appearance that is have been imaged using photometry, ­ubiquitous signatures of chromospheric very different from the granulation pattern spectroscopy, and, only recently, interfer- activity, variable outflows, and winds in across the solar surface. Detailed time- ometry (Figure 3). Here, interferometry spatially unresolved spectra of giant and resolved imaging is needed to constrain has provided a way to unambiguously

36 The Messenger 172 – June 2018 Figure 3. Surface image Miguel Montarges discussed recent stud- of the magnetically ies of red supergiant stars obtained with active star ζ And. the PIONIER instrument in an invited talk, and emphasised the different techniques used to analyse these observations,

Roettenbacher et al., 2016 including intriguing comparisons of inter- ferometric results with spectropolarimetry — as presented earlier in the workshop by Arturo López Ariste and Agnes Lèbre. Claudia Paladini presented stellar surface imaging of the asymptotic giant branch star π1 Gruis in the PIONIER spectral channels (Figure 5; also see Claudia’s article on p. 24). The images of this star are relatively uncontaminated by molecular and dust opacity and show a stellar ­surface characterised by large convective

ESO/K. Ohnaka ESO/K. granulation, constraining the model-­ expected increase in the sizes of convec- tion cells during late phases of stellar evolution (as also discussed earlier during the workshop by Susanne Höfner and Bernd Freytag).

Markus Wittkowski showed PIONIER results for the carbon-rich asymptotic giant branch star R Scl, whose images are dominated by dust seen against the photosphere. This dust is formed in clumps at a few stellar radii, caused by giant convection cells, resulting in large- scale shock fronts, and clumpy molecule Figure 4. VLTI reconstructed view (left) and VLTI He presented a monitoring campaign of and dust formation; this had also been velocity map (right) of the surface of Antares. R Doradus that revealed features on predicted by 3D modelling shown earlier the stellar disc varying on timescales in the workshop by Susanne Höfner. image stellar surfaces without the degen- of a few weeks, showed results for Mira, Markus also showed PIONIER images eracies (for example, across hemispheres) and emphasised the benefit of multi- of a few red supergiant stars, which are experienced by other methods. She wavelength observation campaigns. consistent with the typical contrasts ­discussed recent comparisons of simul- ­predicted from 3D convection models, taneous interferometric and Doppler Keiichi Ohnaka, Miguel Montarges, but with a distribution of convection images. The CHARA array is the only ­Claudia Paladini, and Markus Wittkowski cells across the stellar disc that are not optical facility presently capable of presented recent aperture synthesis randomly distributed but rather appear obtaining the sub-milliarcsecond spatial images of various types of evolved star ­concentrated in certain areas of the resolution necessary to resolve surface obtained with the instruments AMBER stellar disc. features of these stars. and PIONIER at the VLTI. Keiichi Ohnaka, in an invited talk, presented recent For imaging results in the radio/millimetre, Ryan Norris complemented the talks AMBER observations of the red super- Eamon O’Gorman gave an invited talk on based on CHARA results with an over- giant Antares (Figure 4), which succeeded the history of stellar radio imaging, before view of the optimised telescope place- in not only imaging the surface in the showing new results from ALMA (Fig- ments for interferometric imaging. Theo 2.3-micron CO lines in unprecedented ure 6) and the JVLA. Wouter Vlemmings Khouri presented spatially resolved detail, but also for the first time showing went on to present the current status of observations of giant stars obtained with the complex gas dynamics over the their ALMA long-baseline observations the VLT instrument SPHERE in an invited ­surface and atmosphere of the star in a of four asymptotic giant branch (AGB) talk. SPHERE is optimally designed to way that is similar to observations of the stars: W Hya, R Leo, R Dor and Mira. The obtain spatially resolved images of the Sun. The observations showed upwelling line and continuum observations at ALMA closest and apparently largest giant and downdrafting motions of large gas Bands 4, 6 and 7 trace the temperature evolved stars, especially at the shortest clumps in the atmosphere, suggesting and dynamics in their extended atmos- visual wavelengths, where its spatial that mass loss in red supergiants may be pheres. The preliminary analysis confirms ­resolution is about 20 milliarcseconds. launched in a turbulent clumpy manner. a previous detection of a hot spot on

The Messenger 172 – June 2018 37 Astronomical News Wittkowski M. & Humphreys L., Report on the Workshop “Imaging of Stellar Surfaces” ESO/C. Paladini Paladini ESO/C. ALMA (ESO/NAOJ/NRAO)/E. O’Gorman/P. Kervella

Figure 5. The surface of the red giant star π1 Gruis and Mira performed in late 2017, with a Figure 6. ­Betelgeuse, as captured by ALMA. from PIONIER on the VLTI. particular emphasis on HCN.

W Hya, and reveals unexpected lines in Finally, Liz Humphreys described how potential impact on the physical interpre- most of the sources, as well as possible ALMA long-baseline observations had tation of the results. His talk was illustrated fast rotation in the atmosphere of one of revealed an unusual morphology for the with examples of stellar surface imaging the stars. Lynn Matthews described their SiO maser emission towards the binary from real datasets. JVLA and ALMA studies, which reveal system Mira AB. The effect of binary the evolving shapes of the radio photo- companions on the near-circumstellar For the radio to millimetre regime, Bill spheres of AGB stars. The data provide environment of AGB stars is, in general, Cotton gave an invited talk on radio imag- evidence that the shapes of the radio an open question. The ALMA data ing of the envelopes of evolved stars, photospheres of AGB stars change on probed this region of Mira A using SiO paying particular attention to the technical timescales of several months or more. emission. Most importantly, the data differences between radio and optical/ Additionally, the data reveal signatures locate SiO masers with respect to the infrared interferometry. He described how of brightness asymmetries and non-­ star, unlike with lower-frequency obser­ milliarcsecond resolution of very bright, uniformities. The results are consistent vations. They also indicate an impact i.e., non-thermal, emission from molecular with manifestations of large-scale ­irregular of the binary companion on gas within masers in the envelopes of evolved stars convective flows on the stellar surfaces. about 10 stellar radii of Mira A. These can be achieved using VLBI techniques types of studies, using high-frequency with baselines of thousands of kilometres. The application of new imaging tech- SiO masers, can provide a new avenue niques to the interpretation of these data for understanding the influence of binaries was also discussed. Ka Tat Wong out- on AGB mass loss and shaping their Prospects lined a recent study of the non-equilibrium envelopes. chemistry of oxygen-rich AGB stars, Gioia Rau started the session on future ­performed using ALMA. Chemical models prospects with an invited talk about suggest that pulsation-driven shocks Image reconstruction techniques imaging the surfaces of stars from space. propagating from the stellar surfaces of She reviewed results obtained so far from oxygen-rich evolved stars to the dust John Young was invited to provide an space with the benefit of extending the ­formation zone trigger non-equilibrium overview of the various available algo- wavelength coverage, including ultraviolet chemistry in the shocked gas near the rithms for synthesis imaging at visible spectra taken with the International Ultra- star, including the formation of carbon- and infrared wavelengths. He described violet Explorer (IUE), as well as ultraviolet bearing molecules in the stellar winds reconstruction biases that can follow images obtained with the Hubble Space dominated by oxygen-rich chemistry. The from non-optimal choices of regularisation Telescope (HST) of Mira and Betelgeuse. talk focused on observations of IK Tau functions and their strengths, and their She then investigated the prospects for

38 The Messenger 172 – June 2018 infrared imaging with the James Webb Main conclusions and the way ahead highlights and overviews in the different Space Telescope (JWST), and finished sessions. The result was a fairly balanced with a forward look towards space-based A number of recurring themes were representation of invited speakers in large-baseline Fizeau interferometers ­identified over the course of the work- terms of gender, career stage and geo- such as the ultraviolet-optical Stellar shop. It was noted that an increasing graphical distribution. Invited speakers Imager (SI) Vision Mission. synergy arises from interdisciplinary (40% female, 60% male) came from approaches using fundamentally similar ­Belgium (1), Chile (1), ESO (1), France (1), In an invited talk, Dainis Dravins explained techniques developed for solar observa- Germany (1), Ireland (1), Sweden (4), UK the technique of intensity interferometry as tions, spectropolarimetric observations (2), and USA (3). Participants who sub- pioneered by Robert Hanbury Brown and of stars, and spectro-interferometric mitted contributed talks and poster Richard Twiss (Hanbury Brown & Twiss, imaging of stars. Comparisons of detailed ­presentations were accommodated as 1956). He suggested a possible applica- surface features derived at similar epochs requested. In total, the workshop had 60 tion of this technique using the Cherenkov from spectropolarimetry, Doppler imag- participants (25% female, 75% male) from Telescope Array (CTA), enabling spatial ing, and interferometric imaging, both for USA (13), ESO (11), France (8), Sweden­ resolutions of tens of micro­arcseconds, magnetically active stars and red super- (8), Germany (5), Belgium (3), Turkey (2), as well as a possible application using giants, were intriguing and worth continu- UK (2), Poland (1), Austria (1), Spain (1), the mirror segments of ESO’s Extremely ing. Comparing interferometric images Australia (1), Ireland (1), Chile (1), and Large Telescope (ELT). Anita Richards with 3D modelling was also valuable. ­Singapore (1). Among the participants, gave an invited talk on using the full capa- These approaches require time-domain 10% were PhD students (4 female, 2 male). bilities of ALMA, e-MERLIN, the Next- imaging and ideally involve observing We did not ask participants beyond PhD Generation VLA (NG-VLA) or the Square the same sources with multiple facilities students for their career stage, but Kilometre Array (SKA) with long baselines over the same time period. believe that they were evenly distributed to investigate the transport of mass and across the early-, mid-, and late-career energy through the layers above the Another recurring theme was the hypoth- stages. ­photosphere, and to test whether the esis that clumpy mass loss, at least for clumpiness of the wind could be related red supergiants, is related to localised to local ejection of mass from the stellar ejection from the stellar surface. Again, in Acknowledgements surface. order to test this hypothesis, coordinated The other members of the scientific and local multi-wavelength, multi-facility observa- ­organising committees — Stella Chasiotis-Klingner, Antoine Merand concluded the workshop tions are required to follow the transport Bernd Freytag, Xavier Haubois, Tania Johnston, with an invited talk on the VLTI facility of energy and mass from the stellar sur- ­Kateryna Kravchenko, Lisa Löbling, Lynn Matthews, as an imaging machine, outlining how the face to the outermost layers of the atmos- Claudia Paladini, Oskar von der Lühe, and Ke Wang — are warmly thanked for their continuous support. VLTI could evolve to include and operate phere and the wind. While it was generally We are grateful to everybody else who was involved additional telescopes, as well as the accepted that stars, including cool in the preparations for this workshop, and in improvements and limitations related to evolved stars, show chromospheric emis- particular to those who helped make this workshop imaging stellar surfaces. Earlier in the sion, no conclusion was reached about happen in the ESO Supernova Planetarium & Visitor Centre before its official opening, including Sandor workshop, Xavier Haubois had shown the impact of this emission on the mass- Horvath, Tania Johnston, Fabian Reckmann, Jürgen how some improvements were already loss processes in evolved stars. Riesel, Erich Siml, Ana Vukovic, and the teams being implemented, with a description of from the ESO ­education and Public Outreach the newly introduced imaging operations In technical terms, there was an interest- Department, Facility Logistics Transport and catering at ESO. scheme at the VLTI to allow optimised ing suggestion that optical interferometric and adaptive uv plane coverages. imaging could benefit from combining different baseline lengths for the same References Julien Woillez presented the idea of source using different interferometric Hanbury Brown, R. & Twiss, R. Q. 1956, Nature, deploying an agile 12-telescope single- facilities operating at comparable wave- 178, 1046 mode visible interferometer on the lengths. The workshop concluded with a O’Gorman, E. et al. 2017, A&A, 602, L10 Paranal mountain that would be opti- discussion of the impact of stellar surface Ohnaka, K. et al. 2017, Nature, 548, 310 mised to image bright stars. Earlier in imaging on the field of stellar physics in Paladini, C. et al. 2018, Nature, 553, 310 Roettenbacher, R. et al. 2016, Nature, 533, 217 the workshop, Anders Jorgensen and general, as well as on the further develop- Gerard van Belle had considered the ment of interferometric facilities. Navy Precision Optical Interferometer Links (NPOI), proposing its use for the imaging 1 Workshop programme: https://www.eso.org/ of stellar surfaces with the new Classic Demographics sci/meetings/2018/Imaging-Stellar-Surfaces/­ beam combiners, the Visible Imaging program.html System for Interferometric Observations The Science Organising Committee (SOC) (VISION) beam combiners, as well as with consisted of seven members (3 female, its upgrade, the Precision Array of 4 male) from ESO, Germany, Sweden, Large-Aperture New Telescopes for and the USA. The SOC suggested and Image Reconstruction (PALANTIR). voted on invited speakers to present

The Messenger 172 – June 2018 39 Astronomical News DOI: 10.18727/0722-6691/5081

Report on the Workshop Dispersing Elements for Astronomy: New Trends and Possibilities

held at the Civic Aquarium of Milan, Italy, 9–11 October 2017

Andrea Bianco 1 ground-based facilities, the current The focus was mainly on dispersing Rebecca Bernstein 2 Extremely Large Telescope (ELT) projects ­elements based on gratings and prisms; Antonio de Ugarte Postigo 3, 4 provide clear evidence for this, and spec- alternative approaches such as Fabry- Francisco Garzon 5 trographs play an essential role in their Perot interferometry or Fourier-transform Wayne Holland 6 planned instrument suites. Dispersing spectrometers were not considered. The Antonio Manescau 7 elements are at the core of these instru- workshop was organised into the follow- Ramon Navarro 8 ments, since they define the spectral ing three main sessions: Marco Riva 1 ­resolution and dispersion of the spectro- – An overview of the scientific questions graph and hence the final performance to be addressed, both with large and of the instrument. On the other hand, small ground-based astronomical facili- 1 INAF–Osservatorio Astronomico di because of their nature, dispersing ele- ties. In this session, the status of the Brera, Merate, Italy ments are often the least efficient optical three ELTs currently under construction 2 Carnegie Observatories, Pasadena, elements of the whole spectrograph, was presented, including their instru- USA and therefore dominate the final instru- mentation programmes. 3 Instituto de Astrofísica de Andalucía mental throughput. This, of course, also – Properties of dispersing elements for (IAA-CSIC), Granada, Spain holds true for smaller telescopes, which astronomy, their evolution, the issues 4 Dark Cosmology Centre, Niels Bohr can typically address a broad range and constraints of the optical design Institute, University of Copenhagen, of science cases provided they have ade- of spectrographs for large telescopes Denmark quate instrumentation. and, finally, their calibration. 5 Instituto de Astrofísica de Canarias, – Technologies for the production of Tenerife, Spain Starting from the design phase of any ­gratings and prisms. This session was 6 UK Astronomy Technology Centre, spectrograph, it is crucial to be aware of divided according to the different manu- Royal Observatory, Edinburgh, UK the different possibilities that are available facturing technologies and spectral 7 ESO on the market, including those that have range of use of the diffractive elements. 8 NOVA Optical Infrared Instrumentation not specifically been developed for Group, ASTRON, the Netherlands astronomy. Indeed, thanks to new tech- nologies, the possibilities in the field Discussions and outcomes of diffraction gratings and dispersing ele- Astronomical spectrographs play an ments are increasing as a result of a In general, the instrumentation suites important role in addressing some of number of different approaches, for ­proposed for the three ELT projects the biggest challenges in modern example, holography, lithography and are similar, and require a wide range of astronomy. One of the most critical micro-­machining. This is not always easy, spectral and spatial resolutions. They components of any spectrograph is its since the requirements can vary across resemble the instruments developed for dispersing element, since it determines different fields. However, it can be possi- the 8–10-metre-class telescopes and all the resolution and dispersion of the ble to adapt the latest technological face the challenges of wide focal planes spectrograph, and is typically one of advances to specific scientific needs. On and the conservation of the “étendue” — the least efficient optical components the other hand, it is also important for a property of the light used to character- of the instrument. The aim of this work- companies and research institutes that ise the area and angle over which it is shop was to bring together researchers are active in the design and production of spread out. Large-sized gratings/prisms and engineers involved in the design, dispersing elements, and that are involved are required to reach the target resolu- development and construction of in the design of the spectrographs, to tion, but it is important to keep the total ­spectroscopic instrumentation, with understand how to adapt technological size of the instrument within bounds by companies and institutes that produce developments towards becoming feasible means of strategic choices in the optical dispersing elements and associated products for astronomical research. design (through pupil and image slicing). optical components. The forum provided the opportunity to discuss the scientific This workshop 1 brought together The 8–10-metre-class telescopes will needs of future instruments, and to researchers and engineers involved in require new instrumentation and new address the technological challenges the design, development and construc- concepts in the era of the ELTs. One that will allow the development of new tion of spectroscopic instrumentation, example may be the efficient spectro- types of dispersing elements in the as well as companies and institutes that scopic telescopes currently under study, coming years. produce dispersing elements and asso­ which are designed to simultaneously ciated optical components. The forum collect thousands of spectra of targets provided an opportunity to discuss the that are fed from wide field surveys. The In order to adequately address open scientific needs of current and future same approach applies to small- and questions in astronomy, there is a drive instruments and to address the techno- medium-class telescopes, where the sci- for the development of bigger, more logical challenges that will enable the entific cases are often diverse, and which ­sensitive telescopes and instruments — community to progress with the develop- may also need to develop or focus on both ground-based and in space — with ment of new types of dispersing elements specific science cases with very efficient, a very wide spectral range. In respect of in the coming years. dedicated instruments.

40 The Messenger 172 – June 2018 the polarisation. A completely different approach is related to the use of photonic techniques, which exploit the dispersion induced in an optical waveguide system.

Conclusions and Remarks

This very focused workshop was ­characterised by a good mix of science and industry. There were more than 70 participants,­ coming mainly from Europe but also from the USA, Japan and Australia, interacting with representa- tives from 15 companies and research institutes that develop and manufacture dispersing elements and instrumentation.

Figure 1. Workshop participants. large formats, it is now feasible to reach The three days involved many animated sizes of the order of a square metre, and discussions that extended beyond the The dispersing elements for the spectro- these possibilities are worth considering workshop schedule. Indeed, there were graphs have a large set of requirements. when designing future instrumentation. several opportunities to network and dis- Aside from achieving the highest possible cuss a range of related topics, including diffraction efficiency, it is also important specific projects as well as new ideas. to understand and know their dispersion, Dispersing elements for the infrared price, weight/size, availability on the One of the issues identified, was that ­market, ghosts, wavefront error (WFE), In the infrared, immersed gratings have numerous large gratings would be etc. Being able to obtain repeatable and become an interesting option since the required over the next years to satisfy the consistent wavelength calibrations is availability of materials with high refractive requirements of the ELT instrumentation essential to get the best out of the spec- index makes it possible to increase the programmes as well as other existing and trographs, especially for highly stable high- resolution significantly while keeping the future spectroscopic facilities. Although resolution spectrographs. size under control. Moreover, other tech- astronomy is not a big industrial market, nologies, such as VPHGs, are not suitable it is clear that there is room for many The different technologies discussed at for wavelengths above 2.5 µm (new players as the requirements are challeng- the workshop related to the manufacture approaches based on direct laser inscrip- ing. The availability of many new tech­ of diffraction gratings can be summed up tion are being developed to extend the nologies and capabilities will open up under the following headings. range to longer wavelengths). Depending new alternatives, but in order to fully take on the material, different spectral ranges advantage of all of the possibilities, inter- can be covered and non-standard mate- actions between instrument designers, High-performance first-order diffraction rials (like silicon, germanium, zinc selenide, industry and research institutes is crucial. gratings indium phosphate) show excellent proper- This workshop was a successful first step ties and results, especially in terms of in this direction. Volume Phase Holographic Gratings roughness and WFE. (VPHGs) are considered the baseline for Acknowledgements instrumentation in the visible and near- High-precision machining techniques infrared bands, on the basis of the excel- (in particular diamond turning) make it We are grateful for the financial and logistical sup- lent results obtained over the last decade. possible to obtain unconventional gratings port that made this workshop possible. In particular, However, some limitations were appar- we would like to mention the financial support on curved surfaces or freeform gratings. received from ESO, INAF (Italian National Institute of ent, such as their size, WFE, and their The benefit of this could be a simplification Astrophysics), and the Optical Infrared Coordination ­efficiency at high dispersion. Other tech- of the optical design or an improvement Network for Astronomy (OPTICON; an EU Horizon niques are becoming available, in particu- of the capabilities (such as in the case of 2020 research and innovation programme under lar lithographic gratings based on either grant agreement No. 730890). We are also grateful multi-blazed gratings). Moreover, such to the staff of the INAF–Osservatorio Astronomico electron-beam lithography or on hologra- machines are suitable for working on large- di Brera for their consistent support over the course phy. There are some degrees of freedom sized substrates, matching the require- of the workshop. in the structure of the periodic pattern ments of modern telescopes and instru- and in the material, which allow for the mentation. In the case of spectropolarim- Links maximisation of the diffraction efficiency eters, the use of liquid crystal gratings — even in the ultra-violet. As there are can provide interesting advantages, being 1 Workshop web page: http://www.brera.inaf.it/­ markets that require such gratings in very able to control both the dispersion and DispersingElements2017

The Messenger 172 – June 2018 41 Astronomical News DOI: 10.18727/0722-6691/5082

Report on the ESO–Radionet Workshop Submillimetre Single-dish Data Reduction and Array Combination Techniques

held at ESO Headquarters, Garching, Germany, 15–16 March 2018

Carlos De Breuck 1 Peter Teuben 2 Thomas Stanke 1 ESO/L. Calçada ESO/L.

1 ESO 2 University of Maryland, USA

Single-dish submillimetre facilities pro- vide an essential complement to the Atacama Large Millimeter/submillimeter Array (ALMA) interferometry data, but require a set of special observing tech- niques and data reduction software that are different from those applied to radio and millimetre facilities. As there has not been a dedicated workshop to inform the ESO user community about these specific aspects, we decided to organise such a workshop, with the generous financial support of Radionet Figure 1. Workshop participants. Schuller, 2012); and the Interactive Data which made the workshop possible. Language IDL pipeline using the map- making software Scanamorphos for ALMA total power data using the radio ArTéMiS data (­Roussel, 2013; Figure 3). The workshop was attended by 42 par- data processing package Common All of these packages are freely available ticipants (Figure 1), of whom 43% were Astronomy Software Applications (CASA). from either the Institut de Radioastronomie women. The majority of the participants Two additional tutorials showed how to were PhD students or postdocs, likely reduce APEX heterodyne data using vari- reflecting those members of the wider ous alternative software packages: the Figure 2. Example from CLASS tutorial: an on-the- fly data cube of the giant molecular cloud W43 community who are most actively work- Continuum and Line Analysis Single-dish observed in CS with the Swedish Heterodyne Facility ing on this kind of data reduction 1. Software (CLASS; see Figure 2); the Instrument (SHFI) on APEX. Tmb is the main beam Bolometer Array analysis software (BoA; brightness temperature. The workshop began with a general over- view by Thomas Stanke on the challenges of observing with single-dish telescopes (17.68ೀ, 19.81ೀ)(23, 25) 50 at submillimetre wavelengths. In contrast 2 ]) 2 mb ]) T to observing with interferometers, where [ mb

T [ (k the spatially extended sky signal is re­­ 3 (k

0 y solved, for single-dish telescopes, the sky 15 1 1 dominates over the source signal by nsit many orders of magnitude. Moreover, the te In sky signal varies significantly on times- –50 Channel cales on the order of seconds. Most of the 0 0 observing and data reduction techniques therefore need to concentrate on the 100 50 0–50 –100 60 80 100 120 removal of this bright sky emission. Addi-

tional challenges come from the atmos- ) 0.4

50 ]) pheric absorption bands and other instru- 15 ) mb –1 T s [ mental effects. The subsequent lectures (k seconds km presented an overview of the ALMA and y rc ]

Atacama Pathfinder EXperiment (APEX) 0 10 mb T 0.2 nsit n (a [

te io observing capabilities and observing (k

in

strategies, followed by an introduction to ea 5 Ar

the data reduction software used. Mean

Declin at –50 Δ 0 More than half of the time was reserved 0 for (four) hands-on tutorial sessions. 100 50 0 –50 –100 60 80 100 120 Right ascension (arcseconds)V (km s–1) The first tutorial illustrated how to reduce Δ LSR

42 The Messenger 172 – June 2018 Orion A OMC1 — ArTeMiS 350 µm Orion A OMC1 — ArTeMiS 350 µm 300

–5°15ಿ00ೀ –5°15ಿ00ೀ 102

200

–5°20ಿ00ೀ –5°20ಿ00ೀ ion ion 101 Declin at Declin at

–5°25ಿ00ೀ 100 –5°25ಿ00ೀ 1

–5°30ಿ00ೀ –5°30ಿ00ೀ 0 10 –1 5h35m40s 20s 00s 40s 5h35m40s 20s 00s 40s Right ascension (J2000) Right ascension (J2000)

Figure 3. Example from the ArTéMiS data reduction Figure 4. Top left: A channel from tutorial. The image on the left shows the image after an ALMA total power observation running through the basic ArTéMiS IDL pipeline. of CO from a small region in the Note the negative bowls next to the bright emission, Small Magellanic Cloud. Overlayed which are due to the over-subtraction of the sky on this greyscale are the pointing ­signal. The image on the right shows the full reduction centres of the 12-metre array. For using the Scanamorphos pipeline, which uses the one pointing, the true extent of the full redundancy of the data. 12-metre field of view is given as well with the larger green circle. Top right: The reconstructed total Millimétrique (IRAM) website for the power map from the pseudo-­ Grenoble Image and Line Data Analysis visibilities generated from a virtual 2 interferometer emulating the short Software (GILDAS ; Pety, 2005), or the spacings. Lower left: The pure 3 APEX ArTéMiS pages . interferometeric map combining the 7- and 12-metre data. Lower One of the advantages of a single dish right: Combining the total power visibilities with those of the 7- and observation is that it can complement 12-metre data recovers the large- interferometric data by supplying infor- scale flux as well as the fine scale mation corresponding to short spacings structure. The size of each rectan- that are filtered out by the interferometer, gle is ~ 5 × 3 arcminutes and the ­colour scale is in Jy/beam. but that are necessary to recover the 0.54 1.11.7 2.22.8 3.444.55.1 larger-scale emission. It is not uncommon to miss half of the flux in a more extended component when considering only inter- the single dish map with pseudo-visibilities References ferometric data. that can be used in a standard joint Pety, J. 2005, SF2A-2005, ed. Casoli, F. et al., deconvolution method to create images. EdP-Sciences, Conference Series, 721 The majority of the second day in the Roussel, H. 2013, PASP, 125, 1126 workshop was spent on a number of Talk slides, example scripts and example Schuller, F. 2012, SPIE, 8452, 84521T techniques that have been developed and data are linked from the workshop web 1 4 fine-tuned over the past 30 to 40 years, page , the workshop Zenodo repository , Links including a tutorial following the standard as well as via a github repository 5 that example of the M100 spiral galaxy­ using was updated throughout the workshop. 1 Meeting web page: https://www.eso.org/sci/­ CASA, supplemented with two new tech- meetings/2018/SingleDish2018.html 2 IRAM GILDAS website: niques. The default method in CASA is https://www.iram.fr/IRAMFR/GILDAS/ called “feather”, but two new techniques Acknowledgements 3 APEX ArTéMiS pages 3: http://www.apex-telescope. were also highlighted: Short Spacing org/instruments/pi/artemis/data_reduction/ This event received funding from the European 4 Corrections (SSC) — which combines The workshop Zenodo web page: https://zenodo. Union’s Horizon 2020 research and innovation org/communities/sd2018 two images — and the Total Power to ­programme under grant agreement No. 730562. 5 Github repository for the material used in the Visibility tool (TP2VIS) — which replaces ­m e e t i n g : https://github.com/teuben/sd2018

The Messenger 172 – June 2018 43 Astronomical News DOI: 10.18727/0722-6691/5083

Report on the ESO Workshop La Silla Paranal Users Workshop

held at ESO Headquarters, Garching, Germany, 12–14 March 2018

Henri M. J. Boffin 1 Marina Rejkuba 1

1 ESO

In March, ESO organised the La Silla Paranal Users Workshop, providing ­current and future users of its observa- tories with an overview of the available instruments, as well as the most com- monly used tools and processes at ESO, from proposal submission to data reduction and data archive. One full day of the event was dedicated to hands- on data reduction tutorials and one-to- one sessions between participants and ESO staff to work jointly on the issues brought up by the participants. The workshop attracted about 50 on-site participants as well as a dozen remote new Principal Investigators (PIs) per Figure 1. The workshop participants outside the attendees, mostly from Australia. semester submitting proposals to use ESO library. ESO telescopes. As a result, there is a continued need for support and help for bility, scientific productivity and versatility ESO’s ground-based observatories in new users, especially those who are still of the La Silla Paranal Observatory. The Chile serve a very diverse astronomical in the early stages of their careers; this Observatory instrumentation provides community. The La Silla Paranal obser­ was one of the main aims of this fields of view up to 1 degree, and a range vatory offers astronomers the possibility workshop. of spatial resolutions with the smallest of observing with a variety of telescopes, one less than 2 milliarcseconds, and instruments and observing modes, Moreover, ESO has recently signed a a wide spectral coverage (from visible to including both Visitor Mode and Service partnership with Australia and many infrared), which allows astronomers to Mode observations. Furthermore, the ­Australian colleagues were very keen to probe the Universe in complementary Observatory provides support to its learn about ESO. The original idea behind ways. Bruno focused on some examples, users, monitors the quality of all observa- the workshop was to enable face-to-face such as the unique ESO exoplanet tions and the status of its instruments, interaction between users and ESO staff. “machinery”, comprising an unequalled archives data, and for many instruments, However, given the strong interest from suite of instruments: the High Accuracy delivers science grade pipelines and the new Australian community and con- Radial velocity Planet Searcher (HARPS); reduced data products. This level of sup- sidering the cost and time to travel to the Nasmyth Adaptive Optics System port relies on complex machinery that, Garching from Australia, remote participa- Near-Infrared Imager and Spectrograph although efficient, may be daunting for tion via Zoom was set up by our Australian (NACO); the Spectro-Polarimetric High- members of ESO’s user community. ESO colleagues to enable them to follow the contrast Exo­planet REsearch instrument therefore decided to host a three-day various presentations and demonstra- (SPHERE); the VLT Interferometer (VLTI); workshop, in order to present the various tions in real-time. A few other colleagues, the FOcal Reducer/low dispersion tools and services available and, at the mostly from South America, also took ­Spectrograph 2 (FORS2); and, soon, the same time, provide help with improving advantage of this possibility. In total there CRyogenic high-resolution InfraRed the technical aspects of their proposals, were about 50 on-site participants, with Echelle Spectrograph (CRIRES+). He also and with reducing data obtained with a good gender balance (45% female), and emphasised the possibility of performing instruments at La Silla and Paranal. strong participation from another recent long-term observations, for example, ESO member state, Poland. Among the of SN 1987A which has been observed Opening the workshop with a welcome presenters, chairs and tutors, all from over three ­decades at ESO observatories. address, Michael Sterzik, head of the ESO (20 in total), the gender balance was Finally, he also outlined the various pro- Data Management and Operations divi- not quite as good (33% female), but still grammes, workshop series, and publica- sion at ESO, reminded the audience that representative of ESO staff. tions — such as the ESO Messenger — the La Silla Paranal Observatory uses a that allow ESO to maintain a link with its sophisticated and successful operational The Very Large Telescope (VLT) Pro- community. model, at the centre of which is the user gramme Scientist, Bruno Leibundgut, community. This community is continu- presented an overview of ESO and its Henri Boffin presented the impressive ously growing, as there are about 100 observatories, stressing the great flexi­ suite of instruments available at La Silla

44 The Messenger 172 – June 2018 and Paranal and the science that they with observing, and to become familiar web pages contain invaluable material for enable. Astronomers who wish to with the sites and the people running preparing one’s observations. There is observe in the visible or infrared wave- operations. This helps to facilitate later even the possibility that people may be length range are sure to find something interactions when observing in SM. SM overwhelmed by the quantity of informa- that will suit their scientific goals. This observations provide a different educa- tion available. Hence, the need for a will continue to improve, as ESO aims for tional opportunity, as they require the clearer structure; the principal gateway the La Silla Paranal Observatory to main- ability to structure one’s observing strat- for science users is the User Portal. How- tain its world-leading position for at least egy and clearly communicate it to the ever, it is still necessary to review the another 10–15 years by means of con­ Observatory’s staff who will be perform- information contained in the ESO Science tinued instrument upgrades, as well as ing the observations following these web pages, as it is not possible to link the addition of powerful new instruments instructions. The advantages of SM seem to everything relevant directly from the (as Bruno Leibundgut had previously clear to the community. Michael showed User Portal. explained). This concerns not only the that currently the fraction of VM requests VLT but also the VLTI, the 3.5-metre New is only around 15%, and more and more The ESO Science Archive, which was Technology Telescope (NTT), the ESO PIs are requesting SM. presented in detail by Martino Romaniello, 3.6-metre telescope, and the 4-metre is an important resource for astronomers. Visible and Infrared Survey Telescope for The choice of observing mode, SM or Martino explained the various flavours in Astronomy (VISTA). VM, is made at the time of proposal which data can be downloaded, and also preparation. Dimitri Gadotti and Nando the archive services that allow users to Among the impressive advances that Patat gave a talk about writing a success- easily find the science frames and the will enhance the Observatory’s capabili- ful proposal. They strongly suggested associated calibrations needed to reduce ties in the coming years, new observing that everyone read the Call for Proposal data. Around 2.6 million processed sci- modes and future instruments were (CfP) regularly, as this is the contract ence files are present in the archive, ready highlighted: the Echelle SPectrograph between ESO and the PIs. There is no to be analysed and published. However, for Rocky Exoplanet and Stable Spec­ miracle recipe for making a proposal Martino emphasised that the user may troscopic Observations (ESPRESSO); ­successful, but Dimitri gave some guide- need to fully understand the dataset and ­GRAVITY’s astrometric mode; the lines and advice to follow when preparing triple-check the original files and data Multi-AperTure mid-Infrared Spectro- and submitting a proposal — much of it processing steps, especially in cases that Scopic Experiment (MATISSE); the Multi based on common sense. involve unexpected findings. It is not Unit Spectroscopic­ Explorer (MUSE) always safe to blindly accept reduced data. AO ­Narrow Field Mode; CRIRES+; the For those who are successful in getting Enhanced Resolution Imager and Spec- their proposals approved and scheduled, If the science data have not already been trograph (ERIS); the Multi-Object Optical Monika Petr-Gotzens explained how to processed, one needs to use the data and Near-infrared Spectrograph for make the most of the allocated observing reduction process. Wolfram Freudling the VLT (MOONS); the Son Of X-Shooter time, i.e., how to define the right strategy explained how this can be done, using (SOXS); and the Near Infra-Red Planet and carefully plan the observations. A SM ESO pipelines and also the ESO data Searcher (NIRPS). user should submit their observing mate- organiser tools (EsoReflex and the com- rial by the Phase 2 deadline, and check mand line ESO Recipe Execution tool Most of these instruments can be used well in advance if any of the SM rules EsoRex), which help to run the pipeline in Service (or queue) mode (SM) or in cannot be followed — in which case they recipes in a structured way. Wolfram ­Visitor (classical) mode (VM). Francesca would need to request a waiver. Too showed how EsoReflex organises the Primas and Michael Hilker highlighted the often users realise a waiver is needed the data, runs the recipes in order, displays differences between these two observ- day before the Phase 2 deadline and final results and sometimes also interme- ing modes, setting out their pros and start to panic. In SM, it is also crucial to diate products that facilitate the optimisa- cons. For example, VM allows real-time monitor the progress of the scheduled tion of parameters for a given reduction decisions and is best suited to challeng- observations and check the data immedi- step. Once the optimal data reduction ing observations by experts. SM is most ately after they are acquired, so as to be strategy is known, EsoRex offers another appropriate for demanding observing con- able to react quickly in case there is any possibility to script and further automate ditions — for example, transparency and ­need for correction. In addition, Christian data processing. seeing — as the observations are per- Hummel encouraged the audience to formed when the weather conditions fulfil use the interferometric mode of the VLT An important aspect of the workshop the user’s requirements. SM is also best as it is easier than most think. was to provide demonstrations and suited to special observing strategies such ­tutorials of the various tools and services as monitoring a particular target or field. John Pritchard presented an overview of available from ESO. Accordingly, Giacomo the wealth of information available on the Beccari presented the new Phase 2 (p2) There is a clear educational aspect to ESO website, including the possibility of tool used to prepare observations in SM observing in VM and, as Francesca seeing that the lasers are being used at or VM. Jörg Retzlaff and Alberto Micol pointed out, everyone should go at least Paranal while riding the Munich subway presented the archive services, illustrating once to the telescope to get acquainted on the way to the workshop. The Science the forthcoming new interface, and the

The Messenger 172 – June 2018 45 Astronomical News

possibility of making queries in a In the afternoon, participants were able future workshops were also received, ­programmatic way. Lodovico Coccato to interact with ESO staff and discuss with opinions differing, depending on the gave a demonstration of how to reduce topics of their choice, including help with previous experience and knowledge of data with EsoReflex, as well as how to data reduction, help with proposal writing, participants. It is our aim to repeat this use the software Molecfit to remove finding information on ESO web pages, workshop approximately every two years atmospheric signatures from science installing ESO software, help with obser- to promptly address questions from the spectra. Finally, John Pritchard showed vation preparations, and using the Science continuous flow of new users of ESO how to modify Eso­Reflex workflows to Archive either to access data or to return facilities. tailor them to the user’s aims. reduced data to the archive. At registra- tion, participants were asked to indicate One full day of the workshop was dedi- the area of the programme (proposal Acknowledgements cated to hands-on sessions. In the first preparation, observing strategies and We would like to thank Véronique Ziegler for her help part, on Wednesday morning, three tools usage, data reduction) they would with the practical organisation, Stuart Ryder from ­parallel tutorial sessions were held, during like to explore further. Participants were the International Telescopes Support Office (ITSO) which participants were guided in using then split into small groups with overlap- for setting up the remote participation via Zoom, and EsoReflex for three instruments, MUSE, ping interests, or had scheduled one-to- Sandor Horvath and the Information Technology (IT) staff for their help during the workshop. We most the Ultraviolet and Visual Echelle Spectro- one sessions with the ESO staff member warmly thank all speakers and tutors for the great graph (UVES) and X-shooter. These who was best placed to help with their effort they made to provide clear and instructive instruments were chosen as the majority specific topic. talks or demonstrations and to efficiently help the of the participants expressed an interest participants in individual sessions. in them when registering for the work- At the end of the workshop, the organisers shop. In each case, after a first step-by- asked participants to provide feedback, Links step demonstration, the participants and an extremely large number of people, 1 could choose to reduce a set of data more than 50% of the attendees, did so. All presentations as well as some of the video recordings are available on the workshop web ­provided by the organisers or to work on The feedback was unanimously positive page: https://www.eso.org/sci/meetings/2018/ their own data. Two or three tutors were with all respondents saying they would Users-Workshop/program.html available for each session, helping and recommend such a workshop to their advising the participants in this endeavour. colleagues. A few suggestions for similar

DOI: 10.18727/0722-6691/5084 Report on the ESO–NEON Observing School at La Silla Observatory

held at ESO Vitacura, Santiago & La Silla Observatory in Chile, 18 February–2 March 2018

Fernando Selman 1 During the two weeks between 19 Feb- scientific community at Vitacura. In Claudio Melo 1 ruary and 2 March 2018, the Office addition to learning about the observing Giacomo Beccari 1 for Science at Vitacura and the La Silla techniques that were used during Henri M. J. Boffin 1 Observatory were the hosts of the the school, the students also attended Valentin Ivanov 1 ­second ESO/NEON (Network of Euro- several lectures covering the current Eleonora Sani 1 pean Observatories in the North) La Silla and future capabilities of the Atacama Linda Schmidtobreick 1 Observing School. Thanks to the Large Millimeter/submillimeter Array Michel Dennefeld 2 ­generous funding from ESO, the Optical (ALMA), the telescopes at Paranal, and Heidi Korhonen 3 Infrared Coordination Network for the Extremely Large Telescope (ELT), Astronomy (OPTICON), and the La Silla as well as talks on what makes a good Observatory, a group of 20 students, scientific presentation, time manage- 1 ESO consisting of mostly PhD but also some ment, effective proposal writing, and 2 Institut d’Astrophysique de Paris (IAP), advanced MSc students, from different career choices. France parts of the world, were guided by five 3 Dark Cosmology Centre, Niels Bohr ESO tutors. The students prepared Institute, University of Copenhagen, and carried out complex observations, Over the course of three nights at La Silla, Denmark reduced and analysed the data, and the students used the ESO Faint Object finally presented the results to the ESO Spectrograph and Camera (EFOSC2) and

46 The Messenger 172 – June 2018 Figure 1. Left: The ­articipants, organisers, and tutors in front of the NTT telescope. Right: Giacomo Beccari´s group in front of their target.

the infrared spectrograph and imaging Giacomo Beccari guided a group study- nature of the accretors in the observed camera SOFI attached to the New Tech- ing Ha-excess sources in the Orion objects spectroscopically. Similarly, nology Telescope (NTT) as well as the ­nebula and in Chamaeleon. In particular, DFOSC was used to perform broad-band Danish telescope, equipped with the the students acquired low-resolution V, R, I and narrow-band Ha imaging of Danish Faint Object Spectrograph and spectra with EFOSC2 to study the equiva- young stars in Chamaeleon. The images, Camera (DFOSC). Divided into five lent width of the Ha emission line of targeting a number of T Tauri stars with groups, the students worked on a variety 12 young T Tauri stars in Orion. Such Ha emission studied by the Gaia–ESO of astrophysical topics, supported by emission in young stars is typically used Heidi Korhonen at the Danish telescope, to identify ongoing accretion from a Figure 2. Students getting real-life experience at the and by Monica Castillo and Ariel Sanchez protoplanetary disc. The measurements consoles of the NTT (left), and the ­Danish telescope at the NTT 1. allowed the students to confirm the (right).

The Messenger 172 – June 2018 47 Astronomical News Selman F. et al., Report on the “ESO–NEON Observing School at La Silla Observatory”

S1 S2

0.2 )

0.0 3839

S( pec. δ

–0.2

–0.1 0.0 0.1 δG4300

Figure 4. Distribution of CN and CH differential indi- ces for Red-Giant Branch (RGB) stars of the globular cluster NGC 3201 determined by Bruno Dias’s group in the 2016 school. Three groups are identified: the main, well-populated sequence 1 (S1); a second, less populated sequence 2 (S2); and a group of CN-weak/ CH-weak peculiar stars (pec). Mean error bars are displayed in the top right corner. The dashed line was fitted to S1 stars and shifted by 1 magnitude in CH Figure 3. An interesting part of the school is the also monitored the behaviour of the binary to match the S2 and pec stars (Dias et al., 2018). scheduling of the different programmes that com- brown dwarf LUH 16AB over one night. pete for observing slots. Here the groups are trying to coordinate their observations in the La Silla School “War Room”. Eleonora Sani’s group used SOFI to targets was obtained with EFOSC2. Two obtain the spectra of two quasars falling of these objects were classified as in the redshift range 2.5–3.5, i.e., at the Type I a supernova and the third one as survey 2, were used to confirm their peak of activity of cosmic active galactic a galactic nova. The students contributed nature photometrically (i.e., whether or nuclei. The rest-frame optical emission, to writing the corresponding astronomer’s not they are accretors). redshifted into the H- and K-bands, was telegrams. These observations, together observed by means of low-resolution with a specific lecture about the “transient Henri Boffin led a group studying plane- spectra. While the observation of the sky”, aimed to draw the attention of the tary nebulae, using both EFOSC2 and nearer quasar was affected by technical participants to this increasingly important DFOSC to discover the binary stars that problems, the quality of the data for topic, given the development of gravita- lurk at the centre of these majestic and the z ~ 3.5 source allowed the complex tional wave and neutrino detectors and colourful cosmic bubbles. The students profile of the emission lines to be decom- the future arrival of the Large Synoptic were able to obtain the radial velocity posed into narrow and broad compo- Survey Telescope (LSST) in the southern curve and the BVRI photometric light nents. The students were therefore able hemisphere. curves of the binary star inside the plane- to spot the signature of the broad-line tary nebula DS1, and use these to deter- region and to measure its size and the An interesting aspect of these observing mine the parameters of the binary. They gas velocity dispersion, allowing them to schools is that they can lead to publi­ also tried to uncover new binaries in make an estimate of the mass of the cations, even though this is not a require- some other planetary nebulae, providing supermassive black hole of 2–3 108 solar ment. Bruno Dias was a tutor at the useful upper limits as well as impressive masses. school in 2016, and led a group which colour images showing the intricate carried out multi-object spectroscopy ­morphology of these objects. They finally Linda Schmidtobreick’s group worked on using EFOSC2 to study abundances in derived the abundances in one of the the spectral classification of variable star globular clusters. He recently published a planetary nebulae. candidates; low-resolution optical spectra paper with his students entitled “Galactic of the candidates were obtained with or extragalactic chemical tagging for Valentin Ivanov’s group followed the EFOSC2 and cross-correlated with cata- NGC3201? Discovery of an anomalous ­transit of two exoplanets: WASP-43b with logue spectra to obtain the spectral types CN-CH relation” (Dias et al., 2018). Bruno SOFI, and WASP-19b with DFOSC. The of the objects. Together with externally describes the work as follows: data were processed and both transits provided light curves, the variability type were successfully detected. Light curves of each object was discussed. “Globular clusters (GCs) are known to were fitted with publicly available transit host stars with different light-element analysis tools and various parameters of In addition to the above projects, low-­ chemical abundances, such as C, N, O, the planets were measured. The students resolution spectroscopy of three transient Na, Al. In particular, the distributions of

48 The Messenger 172 – June 2018 Figure 5. The students at the school, waiting for a green flash at the end of the first day.

C-N, Na-O are anti-correlated in typical “I want to thank the organisers and Acknowledments GCs. A few anomalous clusters present tutors of the summer school. Both the We would like to express our gratitude to ESO’s multiple sequences of CN-CH anti-­ talks and the research projects were Director General, the La Silla Paranal Observatory correlation, a proxy for C-N. These spe- ­tremendously interesting, and I am sure (LPO) Director and the Director for Science, without cial GCs also share a few other odd they will be very useful in the future. I also whose unconditional support this school would not ­characteristics; this is often interpreted as want to mention what was said among have materialised. We would also like to thank the invited speakers at the school: Michele Cirasuolo, these GCs having originated in dwarf the students, that despite the level of Alain Gilliote, Pascale Hibon, Yara Jaffe, Bruno ­galaxies that were captured and destroyed stress generated, the school exceeded ­Leibundgut, Adele Plunkett, Alain Smette and by the Milky Way. Our results show that the expectations. This type of school Frédéric Vogt. Hans Zinnecker was a special con­ NGC 3201 presents multiple sequences is extremely useful for any astronomer tributor to the school, first with a lecture on star ­formation, and second, contributing to lively dis­ of CN-CH, however it does not show regardless of the area chosen in the cussions and debates about the different topics other anomalous characteristics. We have future. All the activities, from the talks to ­covered — heartfelt thanks to him! The logistical therefore discovered the first GC that is the visit to the observatory motivate aspects of the school were handled by Paulina Jirón neither completely typical nor completely us even more than we already are to con- and María Eugenia Gomez, to whom we extend our deep gratitude. anomalous, which means that the extra- tinue doing research in our PhD.” galactic origin scenario needs revision, and likely requires new stellar evolution It was intense and exhausting but we all References models that can better explain how the feel that the process was well worth the Dias, B. et al. 2018, arXiv:1803.05124 CN-CH anti-correlation forms.” effort. With this and the previous version of the school we have reached a total of The spirit of the school was accurately 40 students who are now familiar with Links summarised by an email from one of the the way ESO does astronomy at the 1 ESO–NEON Observing School: https://www.eso. students at the school, Gabriela Navarro observatories in Chile. More importantly, org/sci/meetings/2018/lasilla_school2018.html from Universidad Andrés Bello (UNAB) in we have been able to share our passion 2 Gaia–ESO Survey: https://www.gaia-eso.eu/ Santiago: and, hopefully, helped the next genera- tion of astronomers.

The Messenger 172 – June 2018 49 Astronomical News DOI: 10.18727/0722-6691/5085

Fellows at ESO

Cyrielle Opitom Cyrielle Opitom

I was born and grew up close to Liège in Belgium. As far as I can remember, I have always been interested in astronomy, space exploration and science in general, even if at the time I could not imagine that I would someday become an astron- omer. I was simply curious to under- stand how things work, from inside the human body to the distant Universe. Later, in high school, I majored in mathe- matics and sciences, and I was lucky to have great maths and physics teachers who allowed me to cultivate and develop my interest in science.

After graduating from high school, I hosted at the La Silla Observatory in first experience at Paranal in addition to ­vacillated between biology and physics, Chile. my previous ones at La Silla (and the but I finally decided to follow my first incomparable beauty of Chile) played ­passion and to start a Bachelor in phys- I really enjoyed this first encounter with an important role in my decision to apply ics, with the intention of specialising in research, especially with such fascinating for an ESO fellowship after the end of astronomy. The choice of university was objects as comets. I was lucky enough my thesis. easy since Liège University, which was to get a grant, so could start a PhD in just next door, was the only one in the Liège, continuing with my Master’s thesis This is how I ended up in Chile, living French-speaking part of Belgium to offer work to study and compare the chemical abroad for the first time. I have never a Masters in space sciences. Because composition of a large number of comets regretted my decision to come to ESO I enjoy sharing my passion for space and observed with the TRAPPIST telescope. Chile and highly appreciate the stimulating astronomy, during my university years Less than two weeks after starting my multi-disciplinary environment and the I had a summer job at the “Euro Space PhD, I flew to La Silla. This was a tech­ opportunity to learn about very different Center” in Belgium, developing activities nical mission, and my first contact with a scientific topics. I also enjoy the freedom aimed at kids and centred on the theme professional telescope was with a screw- that I have to pursue my own research, of space exploration. This was a great driver in my hand. I immediately loved and to try to expand our understanding of experience and encouraged me to con- being at an observatory, especially work- the composition of small bodies of the tinue to do outreach. ing on a small telescope, where you can Solar System. have direct contact with the instrument During my Master’s degree, I took a class you are using. Being part of the TRAPPIST ESO offers a lot of opportunities that I called “Small Bodies of the Solar Sys- team gave me the opportunity to have an would not have elsewhere, especially as tem”. At that time, I became fascinated by overview and get involved in all aspects a young scientist; I get to mentor stu- comets. In addition to being incredibly of the facility, from technical aspects to dents, define my own projects, take up beautiful objects, they are types of fossils scheduling to observing. responsibilities, and organise confer- that allow us to study the history of the ences. Thanks to my duties in Paranal, I Solar System. There is a quote from From the scientific point of view, I am have learned a lot and gained familiarity David Levy, which I think describes com- thankful to my supervisor because I was with new instruments and new tech- ets particularly well: “Comets are like given a lot a freedom to work on the niques. Being assigned to the HAWK-I cats; they have tails and they do precisely ­project my own way as well as pursue infrared imager, I have also participated in what they want”. This summarises how, new ideas. One of the most exciting parts the commissioning of its adaptive optics after studying them for more than a cen- of my thesis was my involvement in the module, working with a really great team. tury, comets remain mysterious objects ground-based support campaign of the The teamwork is something I particularly and keep surprising us; and it is the rea- ESA Rosetta mission. Sending a space appreciate about Paranal. In the future, son I chose comets as the subject of my mission to orbit a comet, and eventually I hope I can continue to do research and Master’s thesis, during which I had the landing on its surface was an incredible keep observing regularly, as I love being chance to work with the TRAnsiting achievement, and it was a fabulous in an astronomical observatory. In any ­Planets and PlanetesImals Small Tele- opportunity to follow the results and new case, I feel lucky to have a family who scope (TRAPPIST) project, which consists developments of the mission while trying always encouraged me to pursue a career of two 60-centimetre telescopes, one to link those to what we were observing in astronomy. It made it so much easier each in the northern and southern hemi- from the ground. It is also in the frame- to get here. spheres. At the time I worked on it, only work of this ground-based campaign that the southern telescope existed, which is I came to Paranal for the first time. This

50 The Messenger 172 – June 2018 Chris Harrison My PhD evolved into using Herschel Space Observatory data to study star formation What a luxury it is to be a professional rates in distant active galaxies. Then I astronomer. I actually get paid to use started working on data that I had been huge telescopes to study supermassive awarded as Principal Investi­gator and black holes destroying galaxies. Yet, began to take charge of my own research. ­perhaps surprisingly, my journey to an During my PhD I also took advantage of ESO Fellowship has not been a clear many exciting opportunities to do out- ­predefined path towards astronomy after reach, for example, delivering planetarium some inspirational events during my shows, giving public talks, and designing childhood. Instead, my route to becoming exhibitions for science festivals. For my an ESO Fellow has been filled with inde- first postdoctoral position, I stayed on at cisiveness, difficult decisions and self- Durham, taking control of large ESO pro- doubt, but also, most importantly, influen- jects involving the K-band Multi-Object tial and supportive people. Spectrograph (KMOS) to study the inter- nal gas kine­matics and dynamics on Beyond wanting to go to university in ­hundreds of distant galaxies; some of my home country of the UK, at the age Durham’s Guaranteed Time on KMOS. of 17, I really did not know what I wanted to do after school. I ordered around 40 With a wife, a one-year old daughter and university prospectuses and spent hours a son on the way, it was difficult to decide flicking through the pages looking for to move the whole family to Germany in inspiration. After a systematic approach Chris Harrison order to take up the ESO Fellowship. to whittle down the options (involving an However, the pull of the fantastic oppor- Excel spreadsheet), I was left with either my wife). However, on getting wind of this, tunities that working at ESO would bring, astrophysics or digital ­multimedia design. Rob Ivison took me into his office and and of living in Munich, were too great to It was almost a flip-of-a-coin decision said, “you should consider a PhD”. Conse- resist. It is such a privilege to be working that resulted in my opting to enroll on an quently, I thought it might be ­sen­sible to at the Headquarters, alongside such a integrated (four-year) Master’s Degree in make some initial enquiries about doing a broad range of people. I now am working astrophysics at the University of PhD when I returned from my travels. This on a range of datasets, from programmes Edinburgh. is when I first met Dave Alexander with his I am leading involving radio interferometry infectious enthusiasm for anything related (eMERLIN; VLA; ALMA), more IFS data After a couple of months of my degree I to supermassive black holes. (ESO/VIMOS; ESO/SINFONI) and X-ray had my first experience of what is now data (Chandra); these are mostly driven widely known as “imposter syndrome” Four months of backpacking in Southeast by the goal to establish the connection and nearly dropped out, believing that I Asia and five months of bush camping between supermassive black holes and didn’t have what it takes. Thanks to sup- in Western Africa gave me a considerable their host galaxies. I am also lucky enough port from my parents and a new friend amount of time to reflect upon what I to have two excellent students working (who ended up being the best man at wanted from life. I concluded that it might alongside me on these projects. my wedding), I decided to try a second be quite fun to undertake a PhD. I was semester. I eventually found my feet and lucky enough that Dave Alexander was I am elated to be working alongside the started to feel a real passion for astron- able to take me on as his student at Supernova coordinator Tania Johnston omy. This was especially true for the ­Durham University. He set me off on on the ESO Supernova Planetarium & third-year research projects, particularly reducing integral field spectroscopy (IFS) Visitor Centre for 25% of my time (my when I was using a small telescope on data from the Near-Infrared Integral Field “ESO project”). I feel honoured to have the roof to make colour-magnitude dia- Spectrometer (NIFS). These data were been part of developing the educational grams of stellar clusters under the super- of distant star-forming galaxies that host workshops and planetarium shows, and I vision of Rob Ivison. During this time, I rapidly accreting black holes, and the am now getting to see them in action, also found great joy in volunteering to goal was to search for evidence of gas since we opened in April of this year. At do outreach at the Visitor Centre at the being expelled from the galaxies. The ESO, I also have the role of being one of Royal Observatory. project was certainly exciting, and I was the fellow representatives, which gives me delighted to have a set of data that the opportunity to improve and refine the Eventually I came to the conclusion that nobody else was working on. Despite Fellowship programme for the other ESO my skills would be best used by becom- this, I briefly felt again that I did not have Fellows. Indeed, this has lately become a ing a physics teacher. I decided to not what it takes to be an astronomer and strong ambition — to ensure that astron- take a full Master’s qualification, but to the other students were much more intel- omy can be a safe, supportive and enjoy- leave after my third year with a Bachelor’s ligent and better researchers. However, able career for everyone. After all, it is a degree and take the “spare” year to go thanks to supportive people around me, luxury to be able to do this job, and we travelling with my girlfriend (who is now I managed to continue. should all be having a fun time doing it.

The Messenger 172 – June 2018 51 Astronomical News Opitom C., Harrison C., Querejeta M., Fellows at ESO

Miguel Querejeta Miguel Querejeta

I was six years old when I first looked through a telescope. It was in a small town called Ezcaray, in the Spanish wine- producing region of La Rioja. I used to spend long summer periods there with my family and those dark night skies always fascinated me; I distinctly remem- ber the feeling of the chilly breeze on a deck chair on the roof terrace, watching shooting stars for hours on end. In such a setting, it seems natural to wonder about the physical nature of those shiny objects — and here I am, more than 20 years later working as a professional astronomer! scopes in La Palma, and it was one of world; the result was a most enjoyable the most memorable summers of my life. and ­productive workshop, leading to a However, the fact that I felt such an early healthy exchange of ideas and triggering fascination for astronomy did not mean At that point, I was fully convinced that new projects and collaborations. that I always wanted to pursue studies in I wanted to embark on a PhD in astro- that direction. As a teenager, I seriously physics by the end of my undergraduate My main research focus at ESO is trying considered the option of studying mathe- studies, and my colleagues from Tenerife to understand the factors that regulate matics, neurobiology, classics, and even informed me about an interesting oppor- the conversion of gas into stars in nearby history of art, which drove my parents a tunity: a Marie Curie Initial Training Net- galaxies; for that goal, I rely on observa- bit crazy. Despite my whims, the support work called Detailed Anatomy of GALaxies tions from interferometers such as the from my parents was always admirable, (DAGAL). This included several positions VLA, NOEMA, and ALMA. This research and they encouraged me to follow my across Europe in the field of nearby is largely pursued in the context of inter- passion for astrophysics. This eventually ­galaxies, and I opted for the project in national collaborations, and working with took me to Madrid, where I studied Phys- Heidelberg: a decision that I did not such a wide range of people makes it ics with Astronomy at the Universidad regret! I conducted my PhD at the Max particularly attractive to me. In addition, Complutense. Planck Institute for Astronomy, super- my functional duties include developing vised by Eva Schinnerer and working outreach material for the ESO Supernova From 2011–2012, I was fortunate enough closely with Sharon Meidt, to whom I Planetarium and Visitor Centre, and I am to spend a year abroad at the University owe a lot. My PhD area was quite broad one of the visiting observers for the APEX of Nottingham through the Erasmus and included investigating how stellar telescope in Chile. scheme, which is a European community mass is distributed in galaxies, molecular action scheme to encourage the mobility gas flows, and nuclear activity, while Ironically, very soon after I started in of university students. I was guided by a spanning a wide range of wavelengths Garching, I was awarded a permanent brilliant tutor, Alfonso Aragón-Salamanca, and techniques. position at the Observatorio Astronómico and I had some excellent lecturers there, Nacional in Madrid, where I will move in such as Mike Merrifield, Chris Conselice, Obtaining an ESO Fellowship straight a few months. I tried my luck with the and Omar Almaini. The atmosphere of the after the PhD was like a dream come application encouraged by colleagues Nottingham Astronomy Group was very true, as it was at the very top of my list from Madrid, honestly thinking that my enthusiastic, and I was able to undertake of preferences. One of the most attractive chances were vanishingly small. But life a year-long research project under the aspects of working at ESO is interacting is full of surprises, and if there is one supervision of Loretta Dunne: using data with such a wide range of people; the thing that I have learned over the years, from the Herschel Space Observatory to atmosphere is extremely friendly, and it is that one should always try, no matter study dusty early-type galaxies — which everyone is very approachable and willing how hard or unlikely something may I very much enjoyed. to help. As an example of the coopera- seem! In retrospect, I can hardly believe tion among ESO Fellows, I would like to the chain of coincidences that has That initial research experience at highlight a workshop that we recently brought me to where I am. I feel most ­Nottingham motivated me to look further organised on galaxy interactions and privileged to work in a field like astronomy, for possible internships, and I obtained a mergers. The entire journey from the ini- which is so exciting and full of inspira- studentship to spend a whole summer at tial seed of a crazy idea to the final event tional people. the Intituto de Astrofísica de Canarias, in was the result of the fruitful collaboration Tenerife. There, I analysed dynamical res- of five ESO Fellows. The conference onances in galaxies with John Beckman took place in Sexten (Italy) in March 2018, and Joan Font. I was stunned by the tele- and it attracted experts from all over the

52 The Messenger 172 – June 2018 Astronomical News DOI: 10.18727/0722-6691/5086

Raymond Wilson, 1928–2018

Martin Cullum 1

1 ESO

Ray Wilson, who worked at ESO for 21 years, died on 16 March 2018. He made an indelible impression on ESO, as well as on the design of modern large tele- scopes worldwide.

Ray was born in Sutton Coldfield in the UK, the youngest of four children. At school he excelled in Latin and history, but made much less impact in mathe­ matics. Nevertheless, he had an early interest in astronomical optics and even built himself a telescope as a teenager. It was his mother who, influenced by a fam- ily friend, later persuaded him to study physics rather than the humanities. She thought — probably rightly — that it would offer better employment possibili- ties. Ray took his first degree in physics at Birmingham University and then went on to Imperial College in London as a postgraduate. It was here that he discov- ered his love of optics and optical design and his PhD thesis, presented in 1953, Carl Zeiss. In 1959, there was no position After five years at Carl Zeiss, Ray was was entitled “The Production of Aspheric free in optical design at Zeiss, and he made head of department and his career Surfaces”. was offered a position in the photographic seemed settled and secure for life, but laboratory, which was responsible for clouds were forming on the horizon. In After leaving Imperial, Ray joined the testing and quality control. This was 1970, German industry was hit by a mas- ­traditional British optical firm Ross and partly theoretical, which suited him, and sive financial crisis. Carl Zeiss was also Company doing, as he said, what he partly practical, which did not, but he seriously affected by this recession and liked doing best — designing optics. was happy to be working for such a pres- many of the staff in Ray’s department Unfortunately, this was not to last long. tigious firm. were made redundant, through no fault In the post-war decades the European of their own. While at Zeiss, Ray had optics industry was in flux. Many tradi- In September 1960, Ray received an already had contact with ESO through tional commercial optics firms in England offer to return to Imperial College London preliminary design contracts for the ESO and France were going bankrupt in the as an assistant lecturer to conduct theo- 3.6-metre telescope. The unpleasant face of German, and later, Japanese retical research on the application of ­situation at Zeiss motivated him to look competition. Ross went bankrupt and computers to optical design. He stayed elsewhere and, in 1972, he was offered Ray moved to the National Physical there until the summer of 1963, and a position as head of the optics group in ­Laboratory (NPL) in Teddington in South then returned once again to Carl Zeiss in ESO’s Telescope Project Division at West London in 1955. Earlier, the NPL Oberkochen, who had offered him his CERN in Geneva. had been very strong in optical design “dream position” in the optical design and aberration theory, but a new man- department for astronomical and analyti- Even several years before Ray moved to ager decided to concentrate on practical cal instruments. ESO, ideas about the active control of optics research which did not appeal to ­telescope optics, now commonly known Ray. So, after three years at the NPL, he In the early 60s there was a small epi- as Active Optics, had been brewing in decided to look for employment in the demic of poliomyelitis in the region of his mind. His collaboration with Gerhard thriving German optical industry. Through Baden-Württemberg where Ray lived, Schwesinger, who had developed an a former German colleague at Ross, Ray and he contracted this disease shortly analytical model of the aberrations intro- was offered a position in a small optics after returning to Zeiss. He was away duced by support errors of primary mir- firm in Trier, called Karl Foitzik. This firm from work for 10 months convalescing rors, furthered these ideas. However, two also went bankrupt within 10 months of and, although he recovered, he was left problems remained: how to measure the Ray’s joining and his next job was with with a slight disability. support errors and how to correct them.

The Messenger 172 – June 2018 53 Astronomical News Cullum M., Raymond Wilson, 1928–2018

The ESO 3.6-metre telescope was Fortunately, Switzerland and Italy pro- Ray Wilson, changed the way future large equipped with a so-called Hartmann vided the solution. In 1982, both coun- tele­scopes would be designed and fully screen. This was a metal plate, the same tries became ESO Member States and validated the decision of the ESO Council diameter as the primary mirror, with an with their entry fees ESO decided to to go ahead with the construction of the array of high precision holes bored in it. build another telescope to ease the load Very Large Telescope (VLT). This was placed just in front of the primary on the already oversubscribed 3.6-metre mirror and a series of extra-focal photo- telescope. At the same time, this pro- Ray was a reluctant manager. He never graphic images were taken at different vided the Organisation with the opportu- strived for power or influence and, telescope positions. After scanning and nity to gain experience with innovative although justly proud of his achievements, analysing these images, the optical aber- ­telescope technologies. Ray Wilson, by was always self-deprecating. But with rations could be estimated. Not only now head of the ESO Telescope Group, his abundant enthusiasm he very effec- was this a cumbersome and risky proce- saw the opportunity to design a modern tively led and inspired the dedicated dure, but the possibilities of correction 3.5-metre alt-azimuth telescope that group of physicists, engineers and tech- with the 3.6-metre telescope were limited eliminated some of the recognised prob- nicians who developed Active Optics by the very heavy and stiff primary mirror. lems with the 3.6-metre. technology at ESO, implementing it on Nevertheless, Ray’s position at ESO the NTT and later — in a more extreme allowed him to develop the idea of Active Ray persuaded the then Director General, form — on the VLT. He was happy to give Optics for future telescopes, and even­ Lodewijk Woltjer, to build the new tele- credit to his colleagues and was always tually to provide solutions to these prob- scope with an actively controlled thin pri- willing to listen and explain. He could talk lems. Even in the late 70s, ESO, along mary mirror. Woltjer agreed under the as naturally to the Director General as with other major observatories, was condition that the New Technology Tele- he could to the ESO janitor and was thus already thinking about the next generation scope (NTT), as it would be known, must greatly respected within the Organisation of giant telescopes. have a performance no worse than the on a personal level as well as for his tech- 3.6-metre telescope even if the active nical expertise. From 1979–1980, Ray spent a year at control did not work as planned. Another La Silla working with the optical group to innovation of the NTT was the free air- During his final three years at ESO, and gain experience in the operation and flow enclosure design. This concept had after he retired in 1993, Ray worked maintenance of large telescopes. This been pioneered at the Multiple Mirror on a two-volume monograph “Reflecting convinced him even more that future tele- ­Telescope on Mt. Hopkins in Arizona and ­Telescope Optics”. These two volumes, scopes should have thin flexible primary differed markedly from that of classical published in 1996 and 1999 respectively, mirrors with an active control system telescope domes, which had small aper- remain classical works on the develop- that would be able to correct optical mis- tures to “protect” the telescope from the ment and design of optical telescopes alignment and compensate for gravita- outside environment. Having a relatively that represent a lasting epitaph to Ray’s tional and thermal mirror distortions. thin primary mirror and effective air flow lifetime achievements. About this time, Ray visited a former stu- through the enclosure allowed the tele- dent colleague from Imperial College, scope — and in particular the primary In the latter part of his career, Ray was Roland Shack, who was now professor at mirror — to be in thermal equilibrium with awarded numerous prizes and honours the Optical Sciences Center in Tucson, the ambient environment, instead of for his contributions to the advancement ­Arizona. Shack had invented a compact being isolated from it. Ray recognised the of telescope technology. These include and efficient optical test device that was importance of this development and the Medal of Geneva University in 1993, based on the classical Hartmann test, it became an important feature of the the Karl Schwarzschild Medal of the but could be mounted directly in the tele- NTT concept. ­German Astronomical Society in 2003, scope focal plane. Ray immediately saw the Chevalier of the French Légion the importance of this device for future The First Light of the NTT in March 1989 d’Honneur in 2004, the Prix Lallemand telescopes and set about having one took place under excellent seeing condi- of the French Academy of Sciences in built at ESO. The device became known tions, allowing the NTT to demonstrate its 2008, the Kavli Prize of the Norwegian as the Shack–Hartmann wavefront sensor. performance to the full. This it certainly Academy of Science and Letters (together When this was later coupled to a CCD did, producing probably the best images with Roger Angel and Jerry Nelson),­ as detector for image readout, ESO had a ever obtained from a ground-based tele- well as the Tycho Brahe Prize of the Euro- practical device to measure telescope scope at that time, and three times better pean Astronomical Society in 2010. aberrations in real time. However, to than had ever been obtained with ESO’s actively correct aberrations would require 3.6-metre telescope. And all of this was He leaves his wife, Anne, and two sons a telescope with a much thinner primary at a third of the cost of the 3.6-metre from his first marriage, Geoffrey and mirror than classical large telescopes like tele­scope! Almost overnight, ESO’s repu- Peter. the ESO 3.6-metre. But to propose the tation as an innovative and leading organ- construction of a very large telescope isation for astronomical research was based on untested technology would established. The overwhelming success have been a giant leap of faith that would of the NTT, founded to a very large hardly be accepted by the ESO Council. extent on the insight and perseverance of

54 The Messenger 172 – June 2018 Astronomical News

Personnel Movements

Arrivals (1 April–30 June 2018) Departures (1 April–30 June 2018)

Europe Europe

Kravchenko, Kateryna (UA) Student Guillard, Nicolas (FR) Student Sagatowski, Jakob (SE) Software Engineer Man, Wing Shan (CN/HK) Fellow Peest, Peter Christian (DE) Student Scholtz, Jan (CZ) Student

Chile Chile

Gallilee, Mark (UK) Mechanical Technical Lead Faez, Robinson (CL) Telescope Instruments Operator Mejia-Restrepo, Julian (CO) Fellow Sánchez Sáez, Paula (CL) Student Wibowo, Ridlo (ID) Student

The ESO Annual Report 2017 is available online now at eso.org/public/announcements/ ann18041/.

The Messenger 172 – June 2018 55 ESO, the European Southern Observa- Contents tory, is the foremost intergovernmental astronomy organisation in Europe. It is Telescopes and Instrumentation supported by 15 countries: Austria, Romaniello M. et al. – Enhanced Data Discovery Services for the ­Belgium, the Czech Republic, Denmark, ESO Science Archive 2 France, Finland, Germany, Italy, the Leibundgut B. et al. – HAWK-I/GRAAL Science Verification 8 Netherlands, Poland, Portugal, Spain, Sweden, Switzerland and the United Astronomical Science Kingdom. ESO’s programme is focused Zhang Z.-Y. et al. – ALMA Constrains the Stellar Initial Mass Function of on the design, construction and opera- Dusty Starburst Galaxies 14 tion of powerful ground-based observ- Ferraro F. R. et al. – MIKiS: the ESO-VLT Multi-Instrument Kinematic Survey ing facilities.­ ESO operates three obser- of Galactic Globular Clusters 18 vatories in Chile: at La Silla, at Paranal,­ Paladini C. et al. – Constraining Convection in Evolved Stars with the VLTI 24 site of the Very Large Telescope, and at Ginski C. et al. – A Planet with a Disc? A Surprising Detection in Llano de Chajnantor. ESO is the Euro- Polarised Light with VLT/SPHERE 27 pean partner in the Atacama Large Milli- meter/sub-millimeter Array (ALMA).­ Astronomical News Currently ESO is engaged in the con- Leibundgut B. & Patat F. – Report on the ESO Workshop struction of the Extremely Large “Planning ESO Observations of Future Gravitational Wave Events” 33 ­Telescope. Wittkowski M. & Humphreys L. – Report on the ESO Workshop “Imaging of Stellar Surfaces” 35 The Messenger is published, in hard- Bianco A. et al. – Report on the Workshop “Dispersing Elements for copy and electronic form, four times a Astronomy: New Trends and Possibilities” 40 year: in March, June, September and De Breuck C. et al. – Report on the ESO–Radionet Workshop December. ESO produces and distrib- “Submillimetre Single-dish Data Reduction and utes a wide variety of media connected­ Array Combination Techniques” 42 to its activities. For further information, Boffin H. M. J. & Rejkuba M. – Report on the ESO Workshop including postal subscription to The “La Silla Paranal Users Workshop” 44 Messenger, contact the ESO education Selman F. et al. – Report on the ESO-Neon Observing School and Public Outreach Department at: at La Silla Observatory 46 Opitom C., Harrison C., Querejeta M. – Fellows at ESO 50 ESO Headquarters Cullum M. – Raymond Wilson, 1928–2018 53 Karl-Schwarzschild-Straße 2 Personnel Movements 55 85748 Garching bei München, Germany Phone +498932006-0 [email protected]

The Messenger: Editors: Gaitee A. J. Hussain, Anna Miotello;­ Graphics, Layout, ­Typesetting: Mafalda Martins; Design, Production: Jutta Boxheimer;­ Proofreading: Peter Grimley; ­www.eso.org/messenger/

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Unless otherwise indicated, all images Front cover: JHK colour-composite image of the central in The Messenger are courtesy of ESO, region of The massive star forming region RCW 38 except authored contributions which from HAWK-I using the ground-layer adaptive optics are courtesy of the respective authors. ­module, enabling a study of the detailed influence of photo­ionisation from massive stars on star formation © ESO 2018 across a wide range of stellar masses down to brown ISSN 0722-6691 dwarfs. Credit: ESO/Muzic et al.