Galaxy Luminosity Functions toz∼1 from DEEP2 and COMBO‐17: Implications for Red Galaxy Formation

The DEEP2 and COMBO-17 surveys are used to study the evolution of theluminosity function of red and blue galaxies to $z \sim 1$. Schechter functionfits show that, since $z = 1$, $M^*_B$ dims by $\sim$ 1.3 mag per unit redshiftfor both color classes, $\phi^*$ of blue galaxies shows little change, while$\phi^*$ for red galaxies has formally nearly quadrupled. At face value, thenumber density of blue galaxies has remained roughly constant since $ z = 1$,whereas that of red galaxies has been rising. Luminosity densities support bothconclusions, but we note that most red-galaxy evolution occurs between our dataand 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 propertiesof local and distant E/S0s. We suggest a ``mixed'' scenario in which some bluegalaxies have their star-formation quenched in gas-rich mergers, migrate to thered sequence with a variety of masses, and merge further on the red sequence inone or more purely stellar mergers. E/S0s of a given mass today will haveformed via different routes, in a manner that may help to explain thefundamental plane and other local scaling laws.