The z < 1.2 optical luminosity function from a sample of ∼410,000 galaxies in Boötes

Using a sample of ∼410,000 galaxies to a depth of I_AB = 24 over 8.26 deg² in the Boötes field (∼10 times larger than the z ∼ 1 luminosity function (LF) studies in the prior literature), we have accurately measured the evolving B-band LF of red galaxies at z < 1.2 and blue galaxies at z < 1.0. In addition to the large sample size, we utilize photometry that accounts for the varying angular sizes of galaxies, photometric redshifts verified with spectroscopy, and absolute magnitudes that should have very small random and systematic errors. Our results are consistent with the migration of galaxies from the blue cloud to the red sequence as they cease to form stars and with downsizing in which more massive and luminous blue galaxies cease star formation earlier than fainter less massive ones. Comparing the observed fading of red galaxies with that expected from passive evolution alone, we find that the stellar mass contained within the red galaxy population has increased by a factor of ∼3.6 from z ∼ 1.1 to z ∼ 0.1. The bright end of the red galaxy LF fades with decreasing redshift, with the rate of fading increasing from ∼0.2 mag per unit redshift at z = 1.0 to ∼0.8 at z = 0.2. The overall decrease in luminosity implies that the stellar mass in individual highly luminous red galaxies increased by a factor of ∼2.2 from z = 1.1 to z = 0.1.