How young are early-type cluster galaxies?: Quantifying the young stellar component in a rich cluster at z=0.41

被引:69
作者
Ferreras, I [1 ]
Silk, J [1 ]
机构
[1] Nucl & Astrophys Lab, Oxford OX1 3RH, England
基金
美国国家航空航天局;
关键词
galaxies; clusters; individual; (Abell; 851; Cl; 0939+4713); galaxies : elliptical and lenticular; cD; galaxies : evolution; galaxies : formation;
D O I
10.1086/312898
中图分类号
P1 [天文学];
学科分类号
0704 ;
摘要
We present a new method of quantifying the mass fraction of young stars in galaxies by analyzing near-ultraviolet (NUV)-optical colors. We focus our attention on early-type cluster galaxies, whose star formation history is at present undetermined. Rest-frame NUV (F300W) and optical (F702W) images of cluster Abell 851 (z = 0.41) using Hubble Space Telescope/WFPC2 allow us to determine an NW-optical color-magnitude relation, whose slope is incompatible with a monolithic scenario for star formation at high redshift. A degeneracy between a young stellar component and its fractional mass contribution to the galaxy is found, and a photometric analysis comparing the data with the predictions for a simple two-stage star formation history is presented. The analysis shows that some of the early-type galaxies may have fractions higher than 10% of the total mass content in stars formed at z similar to 0.5. An increased scatter is found in the color-magnitude relation at the faint end, resulting in a significant fraction of faint blue early-type systems. This would imply that less massive galaxies undergo more recent episodes of star formation, and this can be explained in terms of a positive correlation between star formation efficiency and luminosity.
引用
收藏
页码:L37 / L40
页数:4
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