红色螺旋和尘埃红色星系的STAGES观点：星系团陷落中恒星形成的质量依赖猝灭
The STAGES view of red spirals and dusty red galaxies: Mass-dependent quenching of star-formation in cluster infall
摘要：
利用STAGES数据集的近紫外光学SEDs、24 μ m IR数据和HST形貌，研究了红移约0.17的A901/2星系团复合体中光学被动螺旋星系和尘埃红星系的性质。星团样本是基于COMBO-17红移，均方根精度为sigma_cz~2000 km/sec。我们发现A901/2中的“尘埃红色星系”和“光学被动螺旋”在很大程度上是相同的现象，并且它们以相当大的速度形成恒星，这仅比固定质量的蓝色螺旋低4倍。这颗恒星的形成比蓝色星系更加模糊，其光学特征也很弱。它们主要出现在log M*/Msol=[10，11]的恒星质量范围内，在那里它们构成了星系团中超过一半的恒星形成星系;因此它们是理解星系团中恒星形成猝灭的整体图像的重要组成部分。我们发现，在星系团中的恒星形成星系的平均特定的SFR明显低于在现场，在对比的蓝色星系单独的特定的SFR属性，出现类似的集群和字段。如此丰富的红色螺旋人口最好的解释，如果淬火是一个缓慢的过程和形态转化延迟甚至更多。在log M*/Msol<10时，这样的星系是罕见的，这表明它们的猝灭是快速的，并伴随着形态的变化。我们注意到，边缘上的螺旋起着次要的作用;尽管被灰尘染红，但它们只形成了一小部分独立于环境的螺旋。
英文摘要：
We investigate the properties of optically passive spirals and dusty red galaxies in the A901/2 cluster complex at redshift ~0.17 using restframe near-UV-optical SEDs, 24 micron IR data and HST morphologies from the STAGES dataset. The cluster sample is based on COMBO-17 redshifts with an rms precision of sigma_cz~2000 km/sec. We find that 'dusty red galaxies' and 'optically passive spirals' in A901/2 are largely the same phenomenon, and that they form stars at a substantial rate, which is only 4x lower than that in blue spirals at fixed mass. This star formation is more obscured than in blue galaxies and its optical signatures are weak. They appear predominantly in the stellar mass range of log M*/Msol=[10,11] where they constitute over half of the star-forming galaxies in the cluster; they are thus a vital ingredient for understanding the overall picture of star formation quenching in clusters. We find that the mean specific SFR of star-forming galaxies in the cluster is clearly lower than in the field, in contrast to the specific SFR properties of blue galaxies alone, which appear similar in cluster and field. Such a rich red spiral population is best explained if quenching is a slow process and morphological transformation is delayed even more. At log M*/Msol<10, such galaxies are rare, suggesting that their quenching is fast and accompanied by morphological change. We note, that edge-on spirals play a minor role; despite being dust-reddened they form only a small fraction of spirals independent of environment.
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