The evolving luminosity function of red galaxies

We trace the assembly history of red galaxies since z = 1 by measuring their evolving space density with the B-band luminosity function. Our sample of 39,599 red galaxies, selected from 6.96 deg² of imaging from the NOAO Deep Wide-Field Survey and the Spitzer IRAC Shallow Survey, is an order of magnitude larger, in size and volume, than comparable samples in the literature. We measure a higher space density of z ∼ 0.9 red galaxies than some of the recent literature, in part because we account for the faint yet significant galaxy flux that falls outside of our photometric aperture. The B-band luminosity density of red galaxies, which effectively measures the evolution of ∼L* galaxies, increases by only 36% ± 13% from z = 0 to z = 1. If red galaxy stellar populations have faded by ≃ 1.24 B-band magnitudes since z = 1, the stellar mass contained within the red galaxy population has roughly doubled over the past 8 Gyr. This is consistent with star-forming galaxies being transformed into ≲L* red galaxies after a decline in their star formation rates. In contrast, the evolution of ≃4L* red galaxies differs only slightly from a model with negligible z < 1 star formation and no galaxy mergers. If this model approximates the luminosity evolution of red galaxy stellar populations, then ≃80% of the stellar mass contained within today's 4L* red galaxies was already in place at z = 0.7. While red galaxy mergers have been observed, such mergers do not produce rapid growth of 4L* red galaxy stellar masses between z = 1 and the present day.