The Gaia-ESO Survey – March 2017 progress report

1) Survey observations progress 2) Survey data processing progress 3) Reports to ESO and Phase 3 releases 4) Science projects and publications 5) Catania Conference, meetings, jobs

The Gaia-ESO Public Spectroscopic Survey started more than 5 years ago, and was celebrated with Newsletter Number 1. This is Newsletter 7, where we summarize the progress made during the last year. We remind everyone that all the Survey policy, progress, and activity is recorded on the Survey wiki, available at http://great.ast.cam.ac.uk/GESwiki/GESHome. An account there will keep you up to date. More general information is also available on the public web pages http://www.gaia-eso.eu

1. Survey observations progress

Five years of observations and the originally allocated 300 nights were completed at the end of November 2016. 40 additional nights were granted from ESO to compensate for time lost due to bad weather and technical reasons. 20 of these nights have been scheduled in ESO P98 and have been completed last week with Survey observing run number 55. The remaining 20 nights will be scheduled in ESO P100 (October 2017-March 2018). We anticipate completion of all observations in March 2018.

Almost 60 science open clusters have observations completed, while observations of another 10 or so are planned for P100. The final sample will include about 70 clusters. This is less than the initially planned 90-100 regions; nevertheless, the observed cluster set provides very good sampling of the age-distance-metallicity parameter space. Excellent, unbiased coverage of the cluster sequences and spatial distributions has also been achieved for the majority of the targets, which allows novel science and is crucial to best exploit information from Gaia.

MW observations have focused on covering the widest range of target fields, from the outer thick disk to the inner Galaxy, from the Galactic pole to relatively high extinction low-latitude fields. Several inner Bulge fields have been completed. The parallel UVES star sample looks particularly exciting, covering a very wide range in [Fe/H] and age, with a minimal and well- defined selection function to allow detailed statistical sample analysis. ESO scheduling constraints through competition with VLTI and other scheduled spectroscopic studies of the Galactic Bulge, limited the time available for Gaia-ESO studies of the inner Galaxy. The intended detailed studies of lines of sight at low Galactic latitude through the thin disk will not be implemented.

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Most of the initially planned observations of calibration targets have been completed by now (Pancino et al 2017, Gaia-ESO paper #36). Besides radial velocity standards, the sample of calibrators now includes many benchmark stars (both warm and cool ones), several globular clusters, a few open clusters, and more than 1000 CoRoT red giants. These stars have seismic gravity values from CoRoT. Combined with Gaia-ESO spectra these will not only become excellent calibrators of our astrophysical parameters, but will enable much core Gaia-ESO science. The special analysis process for them is on-going, with results anticipated in the next few months. Similarly, many Kepler-II fields have been observed, with many targets in common with other surveys (GALAH and APOGEE, in particular). These targets represent an exciting calibration sample, with significant scientific potential (see below).

As always, we recall that up to date information on the observing runs, and the survey progress in observed fields is available at the WG0 wiki. A list of the observed open clusters and calibration targets is also available there. A list of cluster targets still to be observed can be found on WG4, where also the relevant information and reports on the clusters and cluster targets can be found.

2. Survey data processing progress

Both Giraffe and UVES data processing pipelines are now routinely and smoothly run after each observing run. The Giraffe pipeline, developed by Jim Lewis at CASU, operates well, although sky subtraction remains challenging in regions affected by significant nebular emission. In this respect we note that sky subtraction for the Carina Nebula hot star fields, for which a special strategy for sky fiber allocation was used, is carried out by Jesus Maiz- Appellaniz, using a specialized pipeline. We also mention that a few problems with radial and rotational velocities (RV and vsini), as well as with the quoted SNR values, were found in the last analysis cycle (iDR4). Whilst the issues with vsini values and SNR have been solved in the current iDR5 cycle, those with RVs are not yet completely sorted out and in a relatively small number of cases, in particular for cool stars with emission lines, unreliable values are still delivered by the pipeline. UVES data are processed at Arcetri using the ESO pipeline. Thanks to the efforts of the team at Arcetri, Lorenzo Morbidelli in particular, and the collaboration with Andrea Modigliani at ESO, the pipeline is considerably more robust and all settings, including the 520nm and 580nm ones, are now processed. [The very few 860nm setting observations are neither processed nor analysed by the spectrum analysis teams.] RV and vsini values are also determined and are generally of good quality. GIRAFFE RV precision meets our goal value: in the best cases, precisions as good as about 250 m/s are achieved (see Jackson et al. 2015: Gaia-ESO paper #37). As for the accuracy, small differences in the zero point are found for both Giraffe and UVES (and of UVES with respect to Giraffe); all RVs are however put on the same scale during the homogenization process.

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iDR5, the fifth full run through the whole Gaia-ESO data cycle, is ongoing, and will provide the astrophysical parameters and element abundance data for the next (DR5) internal data release. iDR5 includes analysis or re-analysis of all spectra observed up to December 2015, adding up to 12400 UVES and 135000 GIRAFFE spectra for 83000 individual objects. The processing cycle iDR5 started at the end of Spring 2016 and included two extensive phases of quality control (QC), for the spectra first, and for the analysis products (stellar parameters) afterwards. The QC phases were very helpful and allowed the identification of a number of issues that were corrected before the full analysis started. The flag system was also improved, allowing us to track problems with the reduction and the analysis and providing an extremely useful tool for survey monitoring. Specifically, a major motivation for the flag and robust QC effort is to ensure that our final Gaia-ESO data set – DR6 – will include every spectrum taken, with a set of flags indicating all QC issues, including cases of too-low signal-noise preventing meaningful spectrum analysis, so that robust statistical analyses of every star targeted for the entire Survey will be possible without bias due to uneven node-level quality censorship selection effects.

The iDR5 run began in July 2016, involving considerable hard work by all the individual nodes and Working Groups, and Working Group leads. The several Working Groups all made good progress, though issues of workload and schedule pressure have meant that the structure of WG10, responsible for Giraffe spectra processing, is being changed. We thank Alejandra Recio-Blanco for her dedicated and considerable efforts over several years in leadership of WG10 up to now. Our process follows Working Group level efforts with homogenization of the astrophysical parameters and metallicity delivered by each Working Group. This has just been completed, thanks to the significant efforts of the WG15 team led by Patrick Francois and including Andy Casey, Francesco Damiani, Anna Hourihane, Laura Magrini, and Clare Worley. The homogenized astrophysical parameters will be delivered to the nodes soon allowing abundance determinations to start.

The abundance run will start by the end of March and the plan is to complete the full cycle during June. The final abundance products should be available through the usual WFAU interface to all Co-Is for scientific verification analyses by mid-July.

As mentioned, there will be a gap in observations between April and October 2017. We will use this time to carry out all the necessary remaining checks and updates on the reduction and analysis pipelines before the next (and final) internal release of spectra and metadata to the spectrum analysis working groups, iDR6, which will happen in late Spring 2018. This release will include all data acquired by Gaia-ESO, plus, as usual, a variety of ESO archival data. The line list and grid of synthetic spectra will be updated for iDR6, and we expect that the nodes will take the opportunity to improve their codes where needed. We anticipate that this final analysis cycle will be completed by Spring 2019. A technical meeting with the spectrum analysis WGs and the nodes will likely be held before the start of iDR6 to discuss all the challenges of this last analysis run, and new options, including the possible use of Gaia DR2 priors.

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Before this final iDR6 processing, we will have available, and distributed for internal survey analyses, the astrophysical parameters and abundances from the special CoRoT and K2 calibration samples. The optimised CoRoT analyses are nearing completion, those for the K2 sample will start shortly. These, together with Gaia DR2 data will allow a significant strengthening of our internal (WG15) homogenization processes, and much complementary information to support you astrophysical analyses.

3. Reports to ESO and Phase 3 releases

Our full annual report on Survey progress to the ESO OPC was delivered for P99 (November 2016) and is available on the wiki home page. These reports provide detailed Survey progress information.

Phase 3 releases: The third Phase III release to ESO started in August 2016 and was completed recently. The data are public at: http://archive.eso.org/wdb/wdb/adp/phase3_spectral/form/ (spectra) http://www.eso.org/qi/ (catalogue)

Reduced spectra, metadata, radial velocities, stellar parameters, and element abundances from our iDR4 cycle were released, based on quality thresholds. Two sets of spectra were released; namely those spectra which were analysed to derive the published iDR4 parameters, and the iDR5 re-reduction of the same spectra. The detailed content of the release can be found in the release description document available at the ESO site and on our wiki. The 4th ESO data release will be based on the current iDR5 processing cycle.

4. Science projects and publications

Science verification and exploitation by the consortium of the recommended astrophysical parameters and abundances released in the previous internal data releases continues to be active and successful. The list of published and in preparation Gaia-ESO papers is available on the wiki. ADS lists 101 publications with Gaia-ESO Survey in the title, half of which are refereed, for a total of almost 1400 citations. These papers address a wide range of science, covering both the top level science goals, and many other more specific topics. We note that the number of papers per year is more or less constant (about 15/year) since our first internal releases, while one may have expected this number to grow in time, when larger/more complete datasets became available. We also note that several of the iDR4 projects anticipated at the Gaia-ESO meeting in Vilnius have not yet converted into papers. This, at least in part, could be due to the fact that people in the consortium not performing the hands- on analysis may not be familiar with the Gaia-ESO products and/or WFAU archive. If this is the case, we encourage you to ask for more technical information from the Cambridge (Anna Hourihane and ClareWorley) and Arcetri (Laura Magrini) members of WG15. They will be happy to help. Also, we are aware that some of the data release description papers, including the overview one(s) by the PIs, are still not ready. We will ensure that those papers will be

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ready for the iDR5 internal release. For the meantime please refer in your papers to the two Messenger articles (Gilmore et al. 2012 and Randich et al. 2013), and to the data release papers that have been published so far. Namely, the UVES pipeline data reduction, WG11, and WG12 analyses, (Sacco et al. 2014, Gaia-ESO paper #13; Smiljanic et al. 2014, Gaia- ESO paper #19; Lanzafame et al. 2014, Gaia-ESO paper #25). In addition, as mentioned, Pancino et al. (2017) summarizes the calibration effort, while Jackson et al. (2015) provides an assessment of the precision of radial and rotational velocities. Finally, Stonkuté et al. (2016, Gaia-ESO paper #53) discuss the Milky Way field selection function.

As always, we remind you to follow the Survey project and publication process summarized in Newsletter #4 (available on the wiki and web pages) and the publication policy document posted on the wiki. Please also note the three week internal timescale to provide comments and request authorship. If you have remaining doubts, please contact either the CoPIs or the coordinators of the College of Readers (Janet Drew, Rob Jeffries, Antonella Vallenari). Do please recall that to meet our open-access requirements, all Survey papers should be posted to astro-ph when accepted, and should use the standard acknowledgement.

Also please recall that, as for our publication policy, copies of papers, as well as presentations at meetings and colloquia at institutes specifically focusing on the Gaia-ESO Survey are to be provided to us to be uploaded on the Survey wiki and webpage.

5. Catania conference, other meetings, jobs.

The fourth consortium all-hands meeting will take place in Catania from September 4-8 2017, with organisation coordinated by Alessandro Lanzafame. Registration is now open at the website (http://www.oact.inaf.it/ges2017/).

The conference will be a chance to discuss our lessons learned from the five analysis cycles and to make concrete plans for iDR6. The meeting will also represent an occasion to discuss the new results and ideas based on iDR5 products. How we can complement Gaia DR2 and Gaia-ESO will be an interesting topic. We encourage all of you to attend the conference. We also recall that a list of meetings related to Gaia-ESO science is maintained on the wiki.

Open positions for PhD studentships and relevant postdoctoral fellowships are advertised on the wiki home page. Feel free to include your own open positions there, and keep looking if you are on the job market.

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Our best regards to all Gaia-ESO Co-I’s

Gerry Gilmore & Sofia Randich

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