An Infrared Survey of Brightest Cluster Galaxies. II. Why are Some Brightest Cluster Galaxies Forming Stars?
An Infrared Survey of Brightest Cluster Galaxies. II. Why are Some Brightest Cluster Galaxies Forming Stars?
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DOI：
10.1086/588212
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发表时间：
2008-03
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影响因子：
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通讯作者：
C. O’Dea;S. Baum;G. Privon;J. Noel-Storr;A. Quillen;Nicholas Zufelt;Jaehong Park;A. Edge;H. Russell;A. Fabian;M. Donahue;C. Sarazin;B. McNamara;J. Bregman;E. Egami
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作者：
C. O’Dea;S. Baum;G. Privon;J. Noel-Storr;A. Quillen;Nicholas Zufelt;Jaehong Park;A. Edge;H. Russell;A. Fabian;M. Donahue;C. Sarazin;B. McNamara;J. Bregman;E. Egami
奎伦等人用斯皮策太空望远镜对62个最明亮的星系团进行了成像观测，这些星系团的核心都有X射线发光的星系团。他们发现，这些辐射源中至少有一半有过量红外辐射的迹象。在这里，我们讨论的红外辐射的性质和它的影响冷核心集群。中红外过量发射的强度与光学发射线的亮度相关。除了活动星系核占主导地位的四个系统外，其余最明亮的星系团中多余的中红外辐射可能与星星的形成有关。分子气体的质量（从CO观测估计）与正常恒星形成星系的红外光度相关。气体耗尽的时间尺度约为1 Gyr。红外线过剩的物理范围与光学发射线星云的物理范围一致。这支持了星星形成发生在与发射线星云有关的分子气体中的假设，并有证据表明发射线星云主要由正在进行的星星形成提供动力。我们发现，从X射线发射估计的质量沉积率（）和从红外光度估计的星星形成率之间的相关性。星星形成率是质量沉积率的1/10到1/100，这表明团内介质的再加热通常非常有效地减少了热相的质量冷却量，但不能完全消除它。
Quillen et al. presented an imaging survey with the Spitzer Space Telescope of 62 brightest cluster galaxies with optical line emission located in the cores of X-ray-luminous clusters. They found that at least half of these sources have signs of excess IR emission. Here we discuss the nature of the IR emission and its implications for cool core clusters. The strength of the mid-IR excess emission correlates with the luminosity of the optical emission lines. Excluding the four systems dominated by an AGN, the excess mid-IR emission in the remaining brightest cluster galaxies is likely related to star formation. The mass of molecular gas (estimated from CO observations) is correlated with the IR luminosity as found for normal star-forming galaxies. The gas depletion timescale is about 1 Gyr. The physical extent of the IR excess is consistent with that of the optical emission-line nebulae. This supports the hypothesis that star formation occurs in molecular gas associated with the emission-line nebulae and with evidence that the emission-line nebulae are mainly powered by ongoing star formation. We find a correlation between mass deposition rates () estimated from the X-ray emission and the star formation rates estimated from the IR luminosity. The star formation rates are 1/10 to 1/100 of the mass deposition rates, suggesting that the reheating of the intracluster medium is generally very effective in reducing the amount of mass cooling from the hot phase but not eliminating it completely.