Working Group for Public Surveys Meeting March 22/23, 1999 (Garching)

The meeting was attended by the following WG members: S. Charlot, S. Cristiani, J. Krautter (chair), K. Kuijken, K. Meisenheimer, Y. Mellier, H. Rottgering, R. Saglia, and P. Schneider.

On the side of ESO, the meeting was attended by: M. Albrecht (part time), D. Baade (part time), L. da Costa, R. Fosbury (part time), M. Nonino (part time), L. Pasquini (part time), R. Rengelink (part time), A. Renzini, P. Rosati (part time), S. Zaggia (part time).

Summary of Meeting

1. Status of the EIS survey. L. da Costa presented an extensive review of the achievements of the EIS project. The large set of multicolor imaging data have been already widely used to select a variety of targets for follow-up work at various facilities. As expected, several VLT proposed programs are using the EIS data, as did some of the UT1 Science Verification observations that were promptly publicly released. The astronomical community from the ESO memberstates (the world community in the case of the HDFS data) has followed the project with wide interest, judging by the visits to the EIS home page over the past two years, and has retrieved substantial amounts of data in various forms such as catalogs, postage stamps and pixel maps. In addition, EIS has also provided a data reduction pipeline which is now being upgraded to handle images from multi-chip cameras and large volumes of data. This pipeline is being developed to support public as well as "private" surveys using the WFI@2.2. After his presentation complete agreement emerged that the survey has reached its goals. The accomplishments have been impressive and on behalf of the WG and the community the chairman thanked the EIS Team for the excellent work performed by them. The WG unanimously agreed that the EIS project had been a success.

2. The WFI at the 2.2m telescope. D. Baade reported about the successful installation of the Wide Field Imager at the 2.2m telescope, which now offers a state-of-the-art instrument for wide field imaging surveys. Preliminary results of reductions of WFI data for the Pilot Survey were shown by L. da Costa which demonstrated the superb image quality of the instrument and what can be expected from the Pilot Survey and the EIS-WFI pipeline. Two areas of concern were identified: 1) the need for the implementation of some sort of Observing Blocks allowing for the advance preparation of observations and the interaction with the telescope control system; and 2) the implementation of the Service Observing mode, in particular for carrying out observations for Public Surveys (see recommendations below).

3. Survey projects with HST. R. Fosbury reported about the medium-term perspectives of large imaging surveys with HST. Public survey projects have played an important role in the scientific return of HST (HDF North and South are the best examples). Their importance will further increase in the future, absorbing a larger fraction of HST time to maximize the cost/benefit ratio. Following the recommendations of the HST Second Decade Committee, some 20-30% of HST time will be invested in large programs (each requiring up to some thousands orbits). Groundbased surveys will have to complement some of the HST surveys, and both will require an enormous effort in development, observation, and operation. The teams involved in the reduction of the data collected in such programs must be well motivated. Public Surveys will have to be perceived as challenging and rewarding to make sure that the scientist with the appropriate profile could be recruited.

4. Pipelines for WFI and VST data reduction. The expected data stream from the WFI@2.2 and, in the future, the VST is tremendous and will strain the data reduction capabilities of most European institutes. M. Albrecht described the plans of the ESO DMD to cope with the problem. On the long term, DMD expects to provide full support to the VST, with an on-line instrument pipeline and a data reduction pipeline running in the framework of the VLT Data Flow System. This effort should be achieved in collaboration with the Omega Cam Consortium, the Capodimonte Observatory (providing the VST), and the Terapix project. A first step towards this goal is the implementation and testing of the Beowolf system, clusters of Linux PC running in parallel, which should greatly enhance the throughput of the reduction pipeline. A Working Group has been appointed to formulate a Memorandum of Understanding to formalize this collaboration and to define the contributions of each group. In the meantime, DMD would continue to provide support to the EIS team in the data distribution and in the implementation and administration of the databases required by the architecture of the EIS-WFI pipeline now near completion. From the discussion, it became clear to the WG that the timescale for the development of the VST pipeline does not address the short-term needs of the WFI and that for the next two years support should be given to the EIS team to consolidate their ongoing work to provide a pipeline for the reduction of WFI data. The WG recognized that the accumulated practical experience of the EIS team will provide valuable information and guidelines to the development of the VST pipeline which should be capitalized. On the other hand, the EIS team should also benefit from the discussions and proposals being considered by the VST collaboration.

5. Ideas for future Public Surveys. Based on the EIS experience the WG agreed that the concept of Public Surveys has been positively accepted by the community as a vital tool to prepare timely observations with the VLT. The WG concurred that it is in the high interest of the community to carry out a second-generation of Public Surveys using with WFI@2.2 and SOFI highly competitive instrumentation. The VLT time-table that future surveys must take into account is: a) Period 64 (Oct99-Mar00), with FORS1 and ISAAC; Period 65 (Apr00-Sep00), with UVES and FORS2 available to the users; b) Period 66 (Oct00-Mar01) VIMOS and possibly FLAMES/GIRAFFE; c) Period 67 (Apr01- Sep01) FLAMES/GIRAFFE and NAOS/CONICA. Note that the VST will become available in Period 68. Therefore, major optical surveys with WFI@2.2 will be possible over the next 4 Periods (64-67).

The WG then started to discuss the responses to the "Call for Ideas" for future Public Surveys. A total of seven "Ideas" were received. The WG reviewed them, considering that 1) the first priority of any Public Survey should be to allow the selection of targets to feed the VLT instruments, and attend the needs of both the stellar and extragalactic ESO communities; 2) the time-table for the availability of the instrumentation at the various VLT units; and 3) the necessity to maintain a competitive edge over surveys planned at other observatories.

The seven responses included the following: 1) Deep multicolor, optical/IR survey, covering several high Galactic latitude fields; 2) Survey aimed at selecting targets for FLAMES/GIRAFFE; 3) Search for variable stars; 4) Optical/IR Imaging Programme for the XMM Serendipitous X-ray Sky Survey 5) Optical imaging of all galaxies within 10 Mpc; 6) Survey of trapezia; 7) Imaging of interacting galaxy clusters.

The WG was unanimous in considering of prime importance for the VLT Science the "DEEP Multicolor Survey" and the "Targets for FLAMES/GIRAFFE". The optical follow-up of deep XMM fields was also considered of great scientific interest, but could be considered in the future only if the corresponding X-ray data were also to become publicly available to the community in a timely fashion. Concerning the search for variable stars, the WG considered that a great opportunity for this science will be offered by the archival research of the accumulated WFI data, as they become publicly available. The WFI offers a unique opportunity for the imaging of nearby galaxies and produce the suggested high-quality atlas; however this meritorious activity would have no wide impact on the science to be done with the VLT, and therefore does not appear to qualify for a Public Survey. Finally, the last two proposals were considered of very limited scientific interest and/or were not sufficiently elaborated. The FLAMES proposal consists of a B, V, I survey of stellar fields to feed targets for GIRAFFE and UVES in multiplex mode, for which accurate astrometry is required for the fibre positioner. The DEEP survey consists of optical/infrared deep imaging of high Galactic latitude fields (possibly some of the EIS fields). Therefore, a Large Proposal for a Public Survey should focus on these two projects, and be submitted to the OPC for Period 64 and following Periods. The WG underlines that such a vital program will be a success only if a number of issues can be timely addressed.

The survey products should include as a minimum the single frame raw, calibration, and calibrated data. As for EIS, it would also be of great utility for the community to have other products to be delivered, including coadded, mosaiced images with astrometric and photometric calibrations, as well as derived catalogs. However, the WG realizes that the large volume of data to be acquired and processed will require an expansion of the current size of the EIS Team, and defers to a future meeting the prioritization of the survey products, when the available resources will be defined by the ESO management to whom the WG makes the following recommendations:

Recommendations:

2. The WG recognizes the great scientific interest of IR imaging surveys as well, and the opportunity offered to ESO by an instrument as efficient as SOFI at the NTT.

3. The WG recommends that - in case the proposal for the deep survey will be accepted by OPC - ESO should issue an Announcement of Opportunity for the IR part of the deep survey to be done by an experienced Group in the community. This group should carry out the survey in close collaboration with the Survey Team at ESO, using the same survey tools, and with the public release of the data following the same policy as for the surveys done at ESO. In any event, the ESO Survey Team should act as a backup.

4. The EIS visitor programme should continue to play an important role in the next two years in: 1) the execution of Public Surveys; 2) the development and operation of the data reduction pipeline; 3) the construction of a calibration database; and 4) the assistance of WFI users in the interim period required for the institutes to prepare themselves to cope with the huge amount of data obtained from such an instrument.

5. The WG greatly appreciates ESO's efforts for EIS and Public Surveys. However, in order to carry out the proposed Public Surveys over a two-year period the EIS team needs a more stable Core Group to ensure the necessary continuity. Such a small Core Group should complement the EIS visitor program (characterized by a frequent, and desirable, turnaround of personnel), and could consist in a mix of external consultants and associates hired for the duration of the project. This can probably be achieved with only a moderate increase in the budget. An effort should be made to make the program appealing to ease the recruitment process, perhaps by tapping resources of institutes involved in the VST program, and using the ongoing surveys as a training ground.

6. The WG appreciates the existing collaboration of the Survey Team with DMD, which should be further expanded in view of the VST.

7. A data flow facility which would allow the use of Observing Blocks should be implemented at the WFI to optimize the observations, improve the bookkeeping and minimize errors which are bound to happen in the current setup.

8. Service observing at the 2.2m telescope with WFI should be offered, in particular for the Public Surveys. This must also involve operational resources to monitor the data quality and the performance of instrument, and to maintain a calibration database. A running deadline for the preparation of OBs for service observations is also suggested.

9. Calibration files taken by any observer must be immediately free for general use.

10. The EIS I filter and a broad U filter should be bought for WFI as well as a B-filter since the B filter currently available shows large color terms.

11. The WG recommends OPC that it should not require detailed objects coordinates for those proposals which make use of Public Survey data which have been taken but not yet released at the time of the proposal deadline. Otherwise one risks wasting one year in highly competitive research areas.

12. The WG reiterates that the scientific productivity of ESO and its VLT would greatly benefit from the development on an IR wide-field facility.

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