Compact groups of galaxies provide a unique environment to study the mechanisms by which star formation occurs amid continuous gravitational encounters. We present 2MASS (JHK) and Spitzer IRAC (3.5-8 μm) and MIPS (24 μm) observations of a sample of 12 Hickson Compact Groups (HCGs 2, 7, 16, 19, 22, 31, 42, 48, 59, 61, 62, and 90) that includes a total of 45 galaxies. The infrared colors of the galaxies in this sample span a range of parameter space, and some trends are apparent in the data. The near-infrared colors of the sample galaxies are largely consistent with being dominated by slightly reddened normal stellar populations. There is also some evidence for a K-band excess in a few cases, which likely indicates the presence of hot dust at or near the sublimation temperature associated with active galactic nuclei or star formation activity. Galaxies that have the most significant polycyclic aromatic hydrocarbon and/or hot dust emission (as inferred from excess 8 μm flux) also tend to have larger amounts of extinction and/or K-band excess and stronger 24 μm emission, all of which suggest ongoing star formation activity. We separate the 12 HCGs in our sample into three types based on the ratio of the group H I mass to dynamical mass. We find evidence that galaxies in the most gas-rich groups tend to be the most actively star forming. Galaxies in the most gas-poor groups tend to be tightly clustered around a narrow range in colors consistent with the integrated light from a normal stellar population. We interpret these trends as indicating that galaxies in gas-rich groups experience star formation and/or nuclear actively until their neutral gas is consumed, stripped, or ionized. The galaxies in this sample exhibit a "gap" between gas-rich and gas-poor groups in infrared color space that is sparsely populated and not seen in the Spitzer First Look Survey sample. This gap may suggest a rapid evolution of galaxy properties in response to dynamical effects. These results suggest that the global properties of the groups and the local properties of the galaxies are connected.
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机译：紧凑的星系组提供了一个独特的环境来研究在不断的引力相遇中恒星形成的机理。我们展示了12个Hickson Compact组（HCG 2、7、16、19、19、22、31、42、48、59， 61、62和90），其中包括总共45个星系。该样本中的星系的红外颜色跨越了一个参数空间范围，并且某些趋势在数据中显而易见。样本星系的近红外颜色在很大程度上与以略微变红的正常恒星群体为主。在某些情况下，也有一些证据表明K波段过剩，这很可能表明在升华温度或与之相关的升华温度附近存在热尘埃，这与活跃的银河核或恒星形成活动有关。具有最显着的多环芳烃和/或热尘埃排放（从过量8μm的通量推断）的星系也趋向于具有更大的消光和/或K波段过量以及更强的24μm排放，所有这些都表明恒星形成活动。根据H I组质量与动态质量之比，我们将样本中的12种HCG分为三种类型。我们发现证据表明，气体最丰富的组中的星系往往是最活跃的恒星形成。气体最贫乏的人群中的星系倾向于紧密聚集在狭窄的范围内，其颜色与正常恒星群体发出的综合光一致。我们将这些趋势解释为表明，富含气体的星系中的星系会活跃地形成恒星和/或核，直到其中性气体被消耗，汽提或电离。此样本中的星系在红外色彩空间中的富气和贫气组之间显示出“间隙”，该间隙稀疏且在Spitzer First Look Survey样本中看不到。这种差距可能表明响应动力学效应，银河特性迅速发展。这些结果表明，这些团的整体性质和星系的局部性质是相互联系的。
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