We present the public release of the stellar mass catalogs for the GOODS-S and UDS fields obtained using some of the deepest near-IR images available, achieved as part of the Cosmic Assembly Nearinfrared Deep Extragalactic Legacy Survey (CANDELS) project. We combine the effort from ten different teams, who computed the stellar masses using the same photometry and the same redshifts. Each team adopted their preferred fitting code, assumptions, priors, and parameter grid. The combination of results using the same underlying stellar isochrones reduces the systematics associated with the fitting code and other choices. Thanks to the availability of different estimates, we can test the effect of some specific parameters and assumptions on the stellar mass estimate. The choice of the stellar isochrone library turns out to have the largest effect on the galaxy stellar mass estimates, resulting in the largest distributions around the median value (with a semi interquartile range larger than 0.1 dex). On the other hand, for most galaxies, the stellar mass estimates are relatively insensitive to the different parameterizations of the star formation history. The inclusion of nebular emission in the model spectra does not have a significant impact for the majority of galaxies (less than a factor of 2 for ∼80% of the sample). Nevertheless, the stellar mass for the subsample of young galaxies (age < 100 Myr), especially in particular redshift ranges (e.g., 2.2 < z < 2.4, 3.2 < z < 3.6, and 5.5 < z < 6.5), can be seriously overestimated (by up to a factor of 10 for < 20 Myr sources) if nebular contribution is ignored.

Although there has been much progress in understanding how galaxies evolve, we still do not understand how and when they stop forming stars and become quiescent. We address this by applying our galaxy spectral energy distribution models, which incorporate physically motivated star formation histories (SFHs) from cosmological simulations, to a sample of quiescent galaxies at < < z 0.2 2.1. A total of 845 quiescent galaxies with multi-band photometry spanning rest-frame ultraviolet through near-infrared wavelengths are selected from the Cosmic Assembly Near-IR Deep Extragalactic Legacy Survey (CANDELS) data set. We compute median SFHs of these galaxies in bins of stellar mass and redshift. At all redshifts and stellar masses, the median SFHs rise, reach a peak, and then decline to reach quiescence. At high redshift, we find that the rise and decline are fast, as expected, because the universe is young. At low redshift, the duration of these phases depends strongly on stellar mass. Lowmass galaxies ( * M M log 9.5 ( ) ) grow on average slowly, take a long time to reach their peak of star formation (4 Gyr), and then the declining phase is fast (2 Gyr). Conversely, high-mass galaxies ( * M M log 11 ( ) ) grow on average fast (2 Gyr), and, after reaching their peak, decrease the star formation slowly (3). These findings are consistent with galaxy stellar mass being a driving factor in determining how evolved galaxies are, with highmass galaxies being the most evolved at any time (i.e., downsizing). The different durations we observe in the declining phases also suggest that low-and high-mass galaxies experience different quenching mechanisms, which operate on different timescales.

Galaxies with stellar masses near M * contain the majority of stellar mass in the universe, and are therefore of special interest in the study of galaxy evolution. The Milky Way (MW) and Andromeda (M31) have present-day stellar masses near M * , at 5 × 10 10 M (defined here to be MW-mass) and 10 11 M (defined to be M31-mass). We study the typical progenitors of these galaxies using the FourStar Galaxy Evolution Survey (ZFOURGE). ZFOURGE is a deep medium-band near-IR imaging survey, which is sensitive to the progenitors of these galaxies out to z ∼ 3. We use abundance-matching techniques to identify the main progenitors of these galaxies at higher redshifts. We measure the evolution in the stellar mass, rest-frame colors, morphologies, far-IR luminosities, and star formation rates, combining our deep multiwavelength imaging with near-IR Hubble Space Telescope imaging from Cosmic Near-IR Deep Extragalactic Legacy Survey (CANDELS), and Spitzer and Herschel far-IR imaging from Great Observatories Origins Deep Survey-Herschel and CANDELS-Herschel. The typical MW-mass and M31-mass progenitors passed through the same evolution stages, evolving from blue, star-forming disk galaxies at the earliest stages to redder dust-obscured IR-luminous galaxies in intermediate stages and to red, more quiescent galaxies at their latest stages. The progenitors of the MW-mass galaxies reached each evolutionary stage at later times (lower redshifts) and with stellar masses that are a factor of two to three lower than the progenitors of the M31-mass galaxies. The process driving this evolution, including the suppression of star formation in present-day M * galaxies, requires an evolving stellar-mass/halo-mass ratio and/or evolving halo-mass threshold for quiescent galaxies. The effective size and SFRs imply that the baryonic cold-gas fractions drop as galaxies evolve from high redshift to z ∼ 0 and are strongly anticorrelated with an increase in the Sérsic index. Therefore, the growth of galaxy bulges in M * galaxies corresponds to a rapid decline in the galaxy gas fractions and/or a decrease in the star formation efficiency.

We explore the evolution of the internal gas kinematics of star-forming galaxies from the peak of cosmic star formation atz 2 to today. Measurements of galaxy rotation velocity V rot , which quantify ordered motions, and gas velocity dispersion s g , which quantify disordered motions, are adopted from the DEEP2 and SIGMA surveys. This sample covers a continuous baseline in redshift over < < z 0.1 2.5, spanning 10 Gyr. At low redshift, nearly all sufficiently massive star-forming galaxies are rotationally supported (By z=2, 50% and 70% of galaxies are rotationally supported at low ( ) stellar mass, respectively. For, the percentage drops below 35% for all masses. From z=2 to now, galaxies exhibit remarkably smooth kinematic evolution on average. All galaxies tend toward rotational support with time, and higher-mass systems reach it earlier. This is largely due to a mass-independent decline in s g by a factor of 3 since z=2. Over the same time period, V rot increases by a factor of 1.5 in low-mass systems but does not evolve at high mass. These trends in V rot and s g are at a fixed stellar mass and therefore should not be interpreted as evolutionary tracks for galaxy populations. When populations are linked in time via abundance matching, s g declines as before and V rot strongly increases with time for all galaxy populations, enhancing the evolution in s V g rot . These results indicate that = z 2 is a period of disk assembly, during which strong rotational support is only just beginning to emerge.