THE CFHT NORTH GALACTIC POLE FAINT GALAXY SURVEY

As part of a study of large-scale structure at intermediate redshifts, a catalog of faint galaxies has been derived for a 2.2 deg2 area (maximum angular extent approximately 2.5-degrees X 2.5-degrees) near the north Galactic pole. The photometric and astrometric calibration methods for the catalog are described in detail; the data comprising the catalog are found to be complete to limiting magnitudes J congruent-to 24 and F congruent-to 23. Galaxy counts and color distributions have been obtained from the catalog. A logarithmic slope of d(log N)/dm = 0.45 was derived for the J bandpass over the magnitude interval 20 less-than-or-equal-to J less-than-or-equal-to 24, whereas d(log N)/dm = 0.37 for the F bandpass (19 less-than-or-equal-to F less-than-or-equal-to 23); these results are in good agreement with previous work. These slopes are determined primarily by the counts at the faintest magnitudes; brighter than J almost-equal-to 22.5 and F almost-equal-to 21.5 the logarithmic slope of the counts is 0.40 in both bands, consistent with the constant mean color that is observed for such galaxies. There is a dramatic difference in the slope of the J and F counts fainter than J almost-equal-to 22.5 and F almost-equal-to 21.5. It is shown that this must imply a change in the properties (number count slope or mean color) of fainter galaxies relative to those at J less-than-or-similar-to 22, and cannot be due solely to the presence of a new population of faint blue objects. The galaxy counts in this catalog match almost perfectly onto counts over the range 15 less-than-or-similar-to J less-than-or-similar-to 20 from the APM survey by Maddox and collaborators, and onto the faint CCD counts by Lilly et al. and Tyson at J greater-than-or-similar-to 23. These three data sets therefore provide a well-defined mean relation for galaxy counts in the J bandpass. No significant variations are seen in the mean number density of galaxies over our fields. This constraint requires that the extent of large-scale inhomogeneities ("sheets") in the galaxy distribution across the line of sight must be larger than approximately 25 h100(-1) Mpc-in reasonable accord with observations of large-scale structure in the CfA survey.