早型星系的恒星形成活动演化研究

摘要

从观测上测定早型星系中恒星形成活动随红移的演化有助于理解这类星系的形成演化.结合GEMS(Galaxy Evolution from Morphology and SEDs)巡天的HST/ACS(Hubble Space Telescope/Advanced Camera for Surveys)高分辨图像和CDFS(Chandra Deep Field South)天区Spitzer、GALEX(Galaxy Evolution Explorer)等多波段数据,基于形态、颜色和恒星质量选出一个0.2≤ z ≤ 1.0红移范围的包含456个早型星系的完备样本.利用stacking技术测量了样本星系紫外与红外平均光度,估计早型星系的恒星形成率.结果显示,早型星系中的恒星形成率较低(＜3 M⊙·yr-1),随红移递减而降低.在红移z=1以来的恒星形成贡献的质量小于15%.星族分析亦肯定大质量早型星系的主体星族形成于宇宙早期(z＞2).%How the star formation activity in early-type galaxies (ETGs) evolves over cosmic time provides observational constraints on the picture of the formation and evolution of ETGs. Using HST/ACS (Hubble Space Telescope/Advanced Camera for Surveys)imaging data from the GEMS (Galaxy Evolution from Morphology and SEDs) survey and multi-band data in the CDFS (Chandra Deep Field South), a complete sample of 456 ETGs within 0.2 ＜ z ＜ 1 is selected based on morphology, color and stellar mass. With stacking technique, the UV and IR average luminosities are derived from GALEX (Galaxy Evolution Explorer) and Spitzer observations and the average star formation rates are estimated. Our results show that the star formation intensities of ETGs are low (SFR ＜ 3 M☉ · yr-1) and decline with decreasing redshift. The total stellar mass contributed by star formation since z = 1 is less than 15％. Stellar population modeling confirms that the bulk of stars in ETGs were formed at early time (z ＞ 2).