PRIMUS: CONSTRAINTS ON STAR FORMATION QUENCHING AND GALAXY MERGING, AND THE EVOLUTION OF THE STELLAR MASS FUNCTION FROM<i>z</i>= 0-1

Abstract

We measure the evolution of the stellar mass function (SMF) from z=0-1 using\nmulti-wavelength imaging and spectroscopic redshifts from the PRism\nMUlti-object Survey (PRIMUS) and the Sloan Digital Sky Survey (SDSS). From\nPRIMUS we construct an i&lt;23 flux-limited sample of ~40,000 galaxies at\nz=0.2-1.0 over five fields totaling ~5.5 deg^2, and from the SDSS we select\n~170,000 galaxies at z=0.01-0.2 that we analyze consistently with respect to\nPRIMUS to minimize systematic errors in our evolutionary measurements. We find\nthat the SMF of all galaxies evolves relatively little since z=1, although we\ndo find evidence for mass assembly downsizing; we measure a ~30% increase in\nthe number density of ~10^10 Msun galaxies since z~0.6, and a &lt;10% change in\nthe number density of all &gt;10^11 Msun galaxies since z~1. Dividing the sample\ninto star-forming and quiescent using an evolving cut in specific\nstar-formation rate, we find that the number density of ~10^10 Msun\nstar-forming galaxies stays relatively constant since z~0.6, whereas the\nspace-density of &gt;10^11 Msun star-forming galaxies decreases by ~50% between\nz~1 and z~0. Meanwhile, the number density of ~10^10 Msun quiescent galaxies\nincreases steeply towards low redshift, by a factor of ~2-3 since z~0.6, while\nthe number of massive quiescent galaxies remains approximately constant since\nz~1. These results suggest that the rate at which star-forming galaxies are\nquenched increases with decreasing stellar mass, but that the bulk of the\nstellar mass buildup within the quiescent population occurs around ~10^10.8\nMsun. In addition, we conclude that mergers do not appear to be a dominant\nchannel for the stellar mass buildup of galaxies at z&lt;1, even among massive\n(&gt;10^11 Msun) quiescent galaxies.\n