MOIRCS DEEP SURVEY. VIII. EVOLUTION OF STAR FORMATION ACTIVITY AS A FUNCTION OF STELLAR MASS IN GALAXIES SINCE z ∼ 3

We study the evolution of star formation activity of galaxies at 0.5 < z < 3.5 as a function of stellar mass, using very deep NIR data taken with the Multi-Object Infrared Camera and Spectrograph on the Subaru telescope in the GOODS-North region. The NIR imaging data reach K similar to 23-24 Vega magnitude and they allow us to construct a nearly stellar-mass-limited sample down to similar to 10(9.5-10) M-circle dot even at z similar to 3. We estimated star formation rates (SFRs) of the sample with two indicators, namely, the Spitzer/MIPS 24 mu m flux and the rest-frame 2800 angstrom luminosity. The SFR distribution at a fixed M-star shifts to higher values with increasing redshift at 0.5 < z < 3.5. More massive galaxies show stronger evolution of SFR at z greater than or similar to 1. We found galaxies at 2.5 < z < 3.5 show a bimodality in their SSFR distribution, which can be divided into two populations by a constant SSFR of similar to 2 Gyr(-1). Galaxies in the low-SSFR group have SSFRs of similar to 0.5-1.0 Gyr(-1), while the high-SSFR population shows similar to 10 Gyr(-1). The cosmic SFR density (SFRD) is dominated by galaxies with M-star = 10(10-11) M-circle dot at 0.5 < z < 3.5, while the contribution of massive galaxies with M-star = 10(11-11.5) M-circle dot shows a strong evolution at z > 1 and becomes significant at z similar to 3, especially in the case with the SFR based on MIPS 24 mu m. In galaxies with M-star = 10(10-11.5) M-circle dot, those with a relatively narrow range of SSFR (less than or similar to 1 dex) dominates the cosmic SFRD at 0.5 < z < 3.5. The SSFR of galaxies that dominate the SFRD systematically increases with redshift. At 2.5 < z < 3.5, the high-SSFR population, which is relatively small in number, dominates the SFRD. Major star formation in the universe at higher redshift seems to be associated with a more rapid growth of stellar mass of galaxies.