The ESO Imaging Survey Project: Status and Pipeline Software

The ESO Imaging Survey (EIS) is a major public imaging survey project being conducted by the European Southern Observatory using several different telescopes and detectors at La Silla in Chile. The primary aim is the identification of samples suitable for more detailed study using the ESO Very Large Telescope (VLT). The first part of the project consisted of two parts: EIS-Wide, an optical survey to moderate depth ( $I_{AB} \mathbin{\lower 3pt\hbox {$\rlap{\raise 5pt\hbox{$\char'074$}}\mathchar''7218$}}24$ ) covering about 20 square degrees; and EIS-Deep, which covered smaller areas of sky to greater depth ( $B_{AB} \mathbin{\lower 3pt\hbox {$\rlap{\raise 5pt\hbox{$\char'074$}}\mathchar''7218$}}26.5$ ) and also included deep near-IR imaging. These surveys are essentially complete and the data are available to users world-wide through the EIS web pages.

Following a successful pilot project with the new Wide Field Imager (WFI) on the 2.2m telescope at La Silla, the EIS team is now engaged in a public imaging survey using the WFI telescope in conjunction with IR imaging using SOFI on the NTT. Three deep fields of one degree square, including the Chandra Deep Field South (CDF-S), are being imaged in the optical along with smaller sub-areas in IR bands. In addition, 160 stellar fields have been imaged as part of the preparations for the use of the FLAMES fibre-feed system for spectrographs on the VLT.

To support the large data volume from this survey and to facilitate its rapid scientific exploitation, a complete end-to-end pipeline system has been developed. Here we give a brief outline of the project so far, and describe the motivation and architecture for the pipeline software.

1. Origins and Historical Evolution

The first phase of the survey was EIS-Wide, which was devoted to moderately deep imaging ( $I_{AB} \mathbin{\lower 3pt\hbox {$\rlap{\raise 5pt\hbox{$\char'074$}}\mathchar''7218$}}24$ ) in BVI in four patches of the southern sky. A total of 17 square degrees in I and smaller areas in B and V were obtained using the EMMI instrument on the ESO NTT. This was complemented by EIS-Deep, which imaged two smaller fields (the Hubble Deep Field South and the Chandra Deep Field South) to greater depth ( $B_{AB} \mathbin{\lower 3pt\hbox {$\rlap{\raise 5pt\hbox{$\char'074$}}\mathchar''7218$}}26.5$ ) and also included near infrared imaging with SOFI. Data were made public in 1998 and described in accompanying papers (Nonino et al. 1999; Olsen et al. 1999a; Prandoni et al. 1999; Zaggia et al. 1999; Olsen et al. 1999b; Benoist et al. 1999; Scodeggio et al. 1999).

In 1999 the Wide Field Imager (WFI) on the 2.2m telescope at La Silla was available. This efficient, wide-field mosaic camera system was used in a pilot project to complete EIS-Wide and image many stellar fields. From November 1999 this was extended into a formal Deep Public Survey which is currently in progress. It covers three fields, each $2 \times 0.5$ degrees in the UBVRI optical bands and covering 450arcmin

at JKs in the near infrared. This is supplemented by 160 stellar fields in preparation for the FLAMES multi-fibre spectrograph to be installed on the VLT. These and the earlier fields are shown on Figure 1.

2. Science Results and Data Examples

**Figure 1:** The Southern Sky showing the positions of the EIS fields along with the Milky Way. The main fields are individually labeled. Asterisks are open cluster, diamonds globular cluster, crosses local group galaxies triangles Milky Way bulge/halo fields and squares Sagittarius Dwarf and LMC/SMC fields.
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**Figure 2:** Example of a small piece of EIS-Wide Patch D. The blue and green channels come from 2.2/WFI B and V data and the red from earlier NTT/EMMI I band imaging.
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3. Early Software Approaches

4. The Current EIS Pipeline

5. Future ESO Sky Surveys

References

Hook, R. N., Bertin, E., da Costa, L., Deul, E., Freudling, W., Nonino, M., & Wicenec, A. 1998, in ASP Conf. Ser., Vol. 145, Astronomical Data Analysis Software and Systems VII, ed. R. Albrecht, R. N. Hook, & H. A. Bushouse (San Francisco: ASP), 320