基于COSMOS(Cosmic Evolution Survey)/UltraVISTAfUltra—deep Visible and Infrared Survey Telescope for Astronomy)场中多波段测光数据,利用质量限选取了红移分布在0〈z〈3.5的星系样本.通过UVJ(U—V和V—J)双色图分类判据将星系分类成恒星形成星系(SFGs)和宁静星系(QGs).对于红移分布在0〈z〈1.5范围内且地〉10^11M⊙的QGs来说,该星系在样本中所占比例高于70%.在红移0〈z〈3.5范围内,恒星形成星系的恒星形成率(SFR)与恒星质量(且以)之间有着很强的主序(MS)关系.对于某一固定的恒星质量帆来说,星系的SFR和比恒星形成率(sSFR)会随着红移增大而增大,这表明在高红移处恒星形成星系更加活跃,有激烈的恒星形成.相对于低质量的星系来说,高质量的SFGs有较低的sSFR,这意味着低质量星系的增长更多的是通过星系本身的恒星形成.通过结合来自文献中数据点信息,发现更高红移(2〈z〈8)星系的sSFR随红移的演化趋势变弱,其演化关系是sSFR∝(1+z)^0.94±0.17.
Utilizing the multi-band photometry catalog of the COSMOS (Cosmic Evolution Survey)/UltraVISTA (Ultra-deep Visible and Infrared Survey Telescope for Astronomy) field, we have constructed a mass-limited sample of galaxies at redshift z ~ 0 - 3.5. Based on the rest-frame UVJ (U-V vs. V-J) color criteria, we classify the sample of galaxies into the star-forming galaxies (SFGs) and the quiescent galaxies (QGs) in different redshift bins. In the redshift range 0 〈 z 〈 1.5, the fraction of QGs with M. 〉 10^11 M⊙ is more than 70%. We find the star formation rate (SFR) and the stellar mass of SFGs show main sequence (MS) relations in all redshift bins. Moreover, the SFR and specific SFR (sSFR) of SFGs increase with redshift at all masses, indicating that the SFGs were much more active on average in the high-redshift universe. Meanwhile, the sSFR of massive SFGs is lower at redshift z ~ 0 - 3.5, implying that the star formation contributes more to the mass growth of low-mass SFGs than to high-mass SFGs. By combining with data from literatures, we find that the evolution of the sSFR with redshift at redshift z ~ 2 - 8 follows sSFR ∝ (1 + z)^0.94±0.17.