2. The data
Although the original intention of EIS was to cover the entire survey area in V and I, this proved impossible due to the bad weather conditions in the period July-December 1997. As a consequence, the observations in the V-band were discontinued after the completion of patch B, to enlarge as much as possible the area covered in I-band. Nevertheless, available V-band images overlap I-band observations over an area of 1.2 and 1.7 square degrees in patches A and B, respectively. Due to varying observing conditions the quality of the data is not uniform over the entire overlap region. This can be seen from the seeing and limiting isophote distributions shown in Papers I and III. This information was used to eliminate regions with significantly shallower limiting magnitudes, due to poor transparency, and the following analysis is restricted to areas of (patch A) and (patch B) square degrees. The median seeing value for all the observations in the area being analyzed is arcsec.
The data were reduced using the EIS reduction pipeline which routinely produces single-frame catalogs, that are associated to produce the so-called even and odd catalogs (see Papers I and II). This procedure has been performed independently for the V and I images, yielding two independent catalogs for each band and each patch. The limiting magnitude for star-galaxy separation in the I-band was established in Papers I and II to be . Brighter than this magnitude only objects with stellarity index less than 0.75 were taken to be galaxies, while all fainter objects were included in the galaxy catalogs. For the V-band the limit for star-galaxy separation was found to be and galaxies were selected following the same procedure. As shown in Papers I and III the 80% completeness limits of the galaxy catalogs extracted from single exposures are typically and .
© European Southern Observatory (ESO) 1999
Online publication: April 19, 1999