Caltech Faint Galaxy Redshift Survey XVI: The Luminosity Function for Galaxies in the Region of the HDF-North to z = 1.5

Abstract

We have carried out a study of the luminosity function (henceforth LF) of galaxies in the region of the HDF-North using our very complete redshift catalog. We solve for the LF at four rest frame wavelengths from 0.24 to 2.2mu. We find that the LFs for quiescent galaxies have shallow faint end slopes, while those of galaxies with detectable emission lines have steeper faint end slopes. Furthermore these slopes are independent of redshift out to z=1.05 for each galaxy spectral grouping and agree well with comparable local determinations. We find that galaxies with strong absorption lines become brighter with z with Q \sim 0.6 at all rest frame bands studied here, where Q = Δ{\rm{log}}[L^*(z)]/Δ{z}, while galaxies with detectable emission lines (i.e. star forming galaxies) show a smaller change in L^* with redshift at all bands, Q ~ 0.3, with Q becoming significantly larger at rest frame 2400A. Passive evolution models of galaxies are in reasonable agreement with these results for absorption line dominated galaxies, while plausible star formation histories can reproduce the behavior of the emission line galaxies. We find the co-moving number density and stellar mass in galaxies to be approximately constant out to z~1.05, and with more uncertainty, to z~1.3. The major epoch(s) of star formation and of galaxy formation must have occurred even earlier. (abridged)