The Norris Survey of the Corona Borealis Supercluster: II. Galaxy Evolution with Redshift and Environment

Abstract

We measure the field galaxy luminosity function (LF) as a function of color and redshift from z = 0 to z = 0.5 using galaxies from the Norris Survey of the Corona Borealis Supercluster. We find that our local r-band LF, when normalized to counts in high galactic latitude fields, agrees well with the local LF measured in the Las Campanas Redshift Survey. Our B-band local LF, however, does not match the B-band LF from the Stromlo/APM survey, having a normalization 1.6 times higher. We see compelling evidence that B-band field galaxy LF evolves with redshift. The evolution is strongest for the population of star-forming galaxies with [OII]3727 rest-frame equivalent widths greater than 10A. The population of red, quiescent galaxies shows no sign of evolution to z = 0.5. The evolution of the LF which we observe is consistent with the findings of other faint galaxy redshift surveys. The fraction of galaxies with [OII] emission increases rapidly with redshift, but the fraction of galaxies with strong Hdelta 4101 absorption, a signature of a burst of star formation, does not. We thus conclude that the star formation in distant galaxies is primarily long-lived. We also compute the LFs of the Corona Borealis supercluster and the A2069 supercluster. The shapes of the two supercluster LFs are broadly similar to the shape of the local LF. However, there are important differences. Both supercluster LFs have an excess of very bright galaxies. In addition, there is a suggestion of an upturn in the LF for galaxies fainter than M(B) = -17 mag. (Abridged from the abstract in the paper.)