标题： MOIRCS深度巡天。 第八。 星系中恒星质量作为恒星形成活动的函数随红移z~3的演化 显示英文标题

标题： MOIRCS Deep Survey. VIII. Evolution of Star Formation Activity as a Function of Stellar Mass in Galaxies since z~3

摘要： 我们利用 Subaru 望远镜在北 GOODS 区域用 MOIRCS（多目标近红外相机光谱仪）获得的非常深的近红外数据，研究了 0.5<z<3.5 范围内星系的恒星形成活动随恒星质量的演化情况。 近红外成像数据达到 K ~ 23-24 颗粒星等，并且使我们可以构建一个接近恒星质量受限样本，即使在 z~3 时也能达到 ~10^{9.5-10}Msun。 我们使用两种指标估算样本的恒星形成率（SFR），即 Spitzer/MIPS 24 微米流量和帧内 2800A 光度。 在固定 Mstar 条件下，SFR 分布随着红移从 0.5 增加到 3.5 而向更高值移动。 在 z>~1 时，更大量的星系显示出更强的 SFR 演化。 我们发现 2.5<z<3.5 的星系在其比恒星形成率（SSFR）分布中表现出双峰性，可以通过约 2 Gyr^{-1}的恒定 SSFR 分为两组。 低 SSFR 组的 SSFRs 约为 0.5-1.0 Gyr^{-1}，而高 SSFR 组则显示约为 10 Gyr^{-1}。 宇宙 SFRD 在 0.5<z<3.5 时由 Mstar = 10^{10-11}Msun 的星系主导，而在 z>1 时，Mstar = 10^{11-11.5}Msun 的大质量星系贡献显示出强烈的演化，并在 z~3 时变得显著，特别是在基于 MIPS 24 微米 SFR 的情况下。 在 Mstar = 10^{10-11.5}Msun 的星系中，具有相对较窄 SSFR 范围（<~1 dex）的星系在 0.5<z<3.5 时主导宇宙 SFRD。 主导 SFRD 的星系的 SSFR 随红移系统地增加。 在 2.5<z<3.5 时，数量相对较少的高 SSFR 群体主导 SFRD。 似乎在更高的红移处宇宙的主要恒星形成与星系的恒星质量更快增长相关。 显示英文摘要

摘要： 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 Multi-Object Infrared Camera and Spectrograph (MOIRCS) on the Subaru telescope in the GOODS-North region. The NIR imaging data reach K ~ 23-24 Vega magnitude and they allow us to construct a nearly stellar mass-limited sample down to ~ 10^{9.5-10} Msun even at z~3. We estimated star formation rates (SFRs) of the sample with two indicators, namely, the Spitzer/MIPS 24um flux and the rest-frame 2800A luminosity. The SFR distribution at a fixed Mstar shifts to higher values with increasing redshift at 0.5<z<3.5. More massive galaxies show stronger evolution of SFR at z>~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 ~2 Gyr^{-1}. Galaxies in the low-SSFR group have SSFRs of ~ 0.5-1.0 Gyr^{-1}, while the high-SSFR population shows ~10 Gyr^{-1}. The cosmic SFRD is dominated by galaxies with Mstar = 10^{10-11} Msun at 0.5<z<3.5, while the contribution of massive galaxies with Mstar = 10^{11-11.5} Msun shows a strong evolution at z>1 and becomes significant at z~3, especially in the case with the SFR based on MIPS 24um. In galaxies with Mstar = 10^{10-11.5} Msun, those with a relatively narrow range of SSFR (<~1 dex) dominates the cosmic SFRD at 0.5<z<3.5. The SSFR of galaxies which 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.