ESO imaging survey

This paper presents multi-passband optical data obtained from observations of the Chandra Deep Field South (CDF-S), located at $\alpha \sim 3^{\rm h} 32^{\rm m}$, $\delta \sim -27^\circ 48^{\prime}$. The observations were conducted at the ESO/MPG 2.2 m telescope at La Silla using the $8{\rm k}\times8{\rm k}$ Wide-Field Imager (WFI). This data set, taken over a period of one year, represents the first field to be completed by the ongoing Deep Public Survey (DPS) being carried out as a part of the ESO Imaging Survey (EIS) project. This paper describes the optical observations, the techniques employed for un-supervised pipeline processing and the general characteristics of the final data set. Image processing has been performed using multi-resolution image decomposition techniques adapted to the EIS pipeline. The automatic processing steps include standard de-bias and flat-field, automatic removal of satellite tracks, de-fringing/sky-subtraction, image stacking/mosaicking and astrometry. Stacking of dithered images is carried out using pixel-based astrometry which enables the efficient removal of cosmic rays and image defects, yielding remarkably clean final images. The final astrometric calibration is based on a pre-release of the GSC-II catalog and has an estimated intrinsic accuracy of $\la$0.10 arcsec, with all passbands sharing the same solution. The paper includes data taken in six different filters (U'UBVRI). The data cover an area of about 0.25 square degrees reaching 5σ limiting magnitudes of $U'_{AB}=26.0$, $U_{AB}=25.7$, $B_{AB}=26.4$, $V_{AB}=25.4, R_{AB}=25.5$ and $I_{AB}=$ 24.7 mag, as measured within a $2 \times FWHM$ aperture. The optical data covers an area of ~0.1 square degrees for which moderately deep observations in two near-infrared bands are also available, reaching $5\sigma$ limiting magnitudes of $J_{AB}\sim23.4$ and $K_{AB}\sim22.6$. The current optical/infrared data also fully encompass the region of the deep X-ray observations recently completed by the Chandra telescope. The optical data presented here, as well as the infrared data released earlier, are publicly available world-wide in the form of fully calibrated pixel and associated weight maps and source lists extracted in each passband. These data can be requested through the URL "http://www.eso.org/eis" .