Mass assembly in quiescent and star-forming galaxies since z=4 from UltraVISTA

We estimate the galaxy stellar mass function and stellar mass density for star-forming and quiescent galaxies with 0.2<z<4. We construct a large, deep (Ks<24) sample of 220,000 galaxies selected using the new UltraVISTA DR1 data release. Our analysis is based on precise 30-band photometric redshifts. By comparing these photometric redshifts with 10,800 spectroscopic redshifts from the zCOSMOS bright and faint surveys, we find a precision of sigma((zp-zs)/(1+zs))=0.008 at i+<22.5 and sigma((zp-zs)/(1+zs))=0.03 at 1.5<z<4. We derive the stellar mass function and correct for the Eddington bias. We find a mass-dependent evolution of the global and star-forming populations, with the low-mass end of the mass functions evolving more rapidly than the high-mass end. This mass-dependent evolution is a direct consequence of the star formation being "quenched" in galaxies more massive than M>10^(10.7-10.9) Msun, while the rapid evolution at the low mass end is explained by the evolution of the specific star formation rate. By deriving the global stellar mass density, we show that galaxies grow in mass twice as quickly at 1<z<4 than at 0.1<z<1. We also confirm that global stellar mass density is lower by 0.2-0.3 dex than the cosmic star formation rate integrated over cosmic time. For the mass function of the quiescent galaxies, we do not find any significant evolution of the high-mass end at z<1, while however we observe a clear flattening of the faint-end slope. From z~3 to z~1, the density of quiescent galaxies increases over the entire mass range. Their comoving stellar mass density increases by 1.5 dex between z~3 and z~1 and by less than 0.2 dex at z<1. Finally, we compare our results with the semi-analytical model and find that they overestimate the density of low mass quiescent galaxies by an order of magnitude.