Galaxy Luminosity Functions to Z ∼ 1: Deep2 vs. Combo-17 and Implications for Red Galaxy Formation

The DEEP2 and COMBO-17 surveys are used to study the evolution of the luminosity function of red and blue galaxies to z ∼ 1. Schechter function fits show that, since z = 1, M∗ B dims by ∼ 1.3 mag per unit redshift for both color classes, φ∗ of blue galaxies shows little change, while φ∗ for red galaxies has formally nearly quadrupled. At face value, the number density of blue galaxies has remained roughly constant since z = 1, whereas that of red galaxies has been rising. Luminosity densities support both conclusions, but we note that most red-galaxy evolution occurs between our data and local surveys and in our highest redshift bin, where the data are weakest. We discuss the implications of having most red galaxies emerge after z = 1 from precursors among the blue population, taking into account the properties of local and distant E/S0s. We suggest a “mixed” scenario in which some blue galaxies have their star-formation quenched in gas-rich mergers, migrate to the red sequence with a variety of masses, and merge further on the red sequence in one or more purely stellar mergers. E/S0s of a given mass today will have formed via different routes, in a manner that may help to explain the fundamental plane and other local scaling laws. Subject headings: Galaxies: distances and redshifts – galaxies: luminosity function – galaxies: evolution