Unveiling the Important Role of Groups in the Evolution of Massive Galaxies: Insights from an Infrared Passive Sequence at Intermediate Redshift
Unveiling the Important Role of Groups in the Evolution of Massive Galaxies: Insights from an Infrared Passive Sequence at Intermediate Redshift
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揭示星系团在大质量星系演化中的重要作用：来自中红移红外被动序列的见解
DOI：
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发表时间：
2008
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影响因子：
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通讯作者：
U.K.
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作者：
D. Wilman;D. Pierini;K. Tyler;S. McGee;A. Oemler;S. Morris;M. Balogh;R. Bower;J. Mpe;Garching;Germany;S. Observatory;Arizona;U. Waterloo;Canada;C. Observatories;Pasadena;U. Durham;U.K.
宇宙中质量最大的星系也是最古老的。为了推翻这种明显的矛盾与层次的增长模型，我们专注于集团规模的晕，主机大多数这些星系。我们的z = 0.4群样本是从hocC 2红移巡天中选取的。利用IRAC观测数据构造了一个质量为M × 1010 M的恒星质量选择样本。一个敏感的中红外（MIR）IRAC颜色被用来隔离被动星系。它产生了一个双峰分布，其中被动星系（突出的形态早期类型）定义了一个紧密的MIR颜色序列（红外被动序列，IPS）。这是由于来自古老恒星群的恒星大气排放。与IPS显著偏离的是尘埃再发射增强了λobs = 8 μm发射的星系。我们称之为红外过剩星系，无论是星星的形成和/或活动星系核的活动。它们包括所有已知的形态晚期类型。与EW[O II]的比较表明，MIR颜色对低水平的活动高度敏感，并使我们能够在高恒星质量下将尘埃活跃星系与被动星系分开。红外过剩星系的比例f（IRE）随M* 而下降，使得f（IRE）在“交叉质量”为Mcr = 1.3 × 1011 M时= 0.5。在我们的光学定义的组样本中，在所有质量下，f（IRE）都存在强烈而一致的赤字，但在M* 1011 M时最为明显。星星形成的抑制必须主要发生在群体中。特别是，f（IRE）与M* 的观测趋势可以解释，如果抑制M*<$1011 M星系主要发生在集团环境。这一点可以通过千禧年模拟得到的模拟星系目录得到证实。通过这种方式，f（IRE）中的质量依赖演化（缩小）可以仅仅由宇宙中的结构增长驱动，因为更多的星系随着宇宙时间被吸积成群大小的晕。
The most massive galaxies in the universe are also the oldest. To overturn this apparent contradiction with hierarchical growth models we focus on the group-scale halos that host most of these galaxies. Our z ∼ 0.4 group sample is selected in redshift space from the CNOC2 redshift survey. A stellar mass-selected M*≳ 2 × 1010 M☉ sample is constructed using IRAC observations. A sensitive mid-infrared (MIR) IRAC color is used to isolate passive galaxies. It produces a bimodal distribution, in which passive galaxies (highlighted by morphological early types) define a tight MIR color sequence (infrared passive sequence, IPS). This is due to stellar atmospheric emission from old stellar populations. Significantly offset from the IPS are galaxies where reemission by dust boosts emission at λobs = 8 μm. We term them infrared excess galaxies, whether star formation and/or AGN activity are present. They include all known morphological late types. Comparison with EW[O II] shows that MIR color is highly sensitive to low levels of activity and allows us to separate dusty active from passive galaxies at high stellar mass. The fraction of infrared excess galaxies, f(IRE) , drops with M*, such that f(IRE) = 0.5 at a “crossover mass” of Mcr ∼ 1.3 × 1011 M☉. Within our optically defined group sample there is a strong and consistent deficit in f(IRE) at all masses, but most clearly at M*≳ 1011 M☉. Suppression of star formation must mainly occur in groups. In particular, the observed trend of f(IRE) with M* can be explained if suppression of M*≳ 1011 M☉ galaxies occurs primarily in the group environment. This is confirmed using a mock galaxy catalog derived from the millenium simulation. In this way, the mass-dependent evolution in f(IRE) (downsizing) can be driven solely by structure growth in the universe, as more galaxies are accreted into group-sized halos with cosmic time.