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CCD multicolor imaging of over 25 000 faint galaxies in 12 random high-latitude fields reveals strong evidence for color and luminosity evolution. Deep images in several bands from 0. 36 to 1 micron enable studies of galaxies undergoing evolution at redshifts up to 7 in a zero-dust universe. Fainter than 27th BJ_ magnitude the sky becomes confusion limited in galaxies. Galaxy counts at 25th BJ_ magnitude are a factor of 5-15 above no-evolution models. The differential number counts of galaxies log N (m) are found to vary with magnitude as 0. 3 I to 0. 45 BJ_, ruling out a local origin of these faint galaxies. A strong blueing trend is seen for the fainter galaxies, suggesting that the UV excess from massive star formation in these evolving galaxies has been redshifted into the blue band. The extragalactic background light is computed explicitly from the number-magnitude counts. No evidence is found for 10-30 arcsec extended primeval objects down to 30 BJ_ mag arcsec^-2^; however, cleaning these "bright" objects and smoothing reveals occasional structures as large as 30 arcsec down to 32 BJ_ mag arcsec^-2^. Mild and continuous evolution of field galaxies seems to have occurred, and any global burst phase at z < 6 must have been shrouded in dust. If the universe is not optically thick in dust at redshifts of 2-3, our number-count and color data are most consistent with formation of the first galaxies beginning at redshifts larger than 4 (although significant formation could continue to the present epoch). These data are not consistent with some dark matter theories, if galaxy-sized perturbations were gaseous at formation. If these galaxies are at redshifts of 1-3, as their colors, scale, and surface brightness suggest, then a low OMEGA is favored.
J. A. Tyson (Fri,) studied this question.