INITIAL GALAXY COUNTS FROM DIGITIZED POSS-II

In our first analysis of the Digitized Second Palomar Observatory Sky Survey (DPOSS), we examine galaxy counts on an overlapping set of four survey fields near the North Galactic Pole, in both the J and F passbands. Through detailed simulations of a subset of these data, we were able to analyze systematic aspects of our detection and photometric procedures, as well as optimize them. We discuss how we calibrate the plate magnitudes to the Gunn-Thuan g and r photometric system using CCD sequences obtained in a program devoted expressly to calibrating DPOSS. Our technique results in an estimated plate-to-plate zero-point standard error of under 0.10m in g and below 0.05m in r, for J and F plates, respectively. Using the catalogs derived from these fields, we compare our differential galaxy counts in g and r with those from recent Schmidt plate surveys as well as predictions from evolutionary and nonevolutionary (NE) galaxy models. While we find some differences between our measurements and others, particularly at the bright end, we find generally good agreement between our counts and recent NE and mild evolutionary models calibrated to consistently fit bright and faint galaxy counts, colors, and red-shift distributions. The consistency of our results with these predictions provides additional support to the view that very recent (z<0.1) and exotic galaxy evolution, or nonstandard cosmology, may not be necessary to reconcile these diverse observations with theory. © 1995 American Astronomical Society.