The Insignificance of Global Reheating in the A1068 Cluster: Multiwavelength Analysis
The Insignificance of Global Reheating in the A1068 Cluster: Multiwavelength Analysis
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DOI：
10.1086/380114
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发表时间：
2003-10
期刊：
影响因子：
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通讯作者：
B. McNamara;B. McNamara;M. Wise;S. Murray
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文献类型：
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作者：
B. McNamara;B. McNamara;M. Wise;S. Murray
在本文和Wise，McNamara和Murray的配套论文中，我们对A1068星系团进行了详细的多波长研究，并使用这些数据来测试星系团的冷却和能量反馈模型。该星团的近紫外和红外图像显示，cD星系正在经历星星形成的速度约为20-70百万年-1在过去的100万年。尘埃星暴集中在cD星系的核心，并在60 kpc的星系结构中投射到它的晕中。在Wise，McNamara和Murray的钱德拉X射线图像中显示了一个陡峭的温度梯度，从超过120 kpc的大约4.8 keV下降到星系内部10 kpc的大约2.3 keV，那里是星暴的高峰。超过95%的紫外线和Hα光子与星暴有关，它们来自于冷却时间非常短（约1亿年）的keV气体覆盖的区域，这与通过冷却星团内介质中的冷凝而形成的星星所预期的一样。然而，钱德拉光谱与1.14 - 1.45亿转/年的速率是一致的，但不需要冷却，比ROSAT观测站发现的速率低几个系数。在中心星暴附近的局部冷却速率为400兆年-1，这是一致的星星的形成率确定的U-波段和红外数据。我们考虑了与星暴相关的射电源、热传导和超新星爆炸对团内介质的能量反馈。我们发现，在A1068中，射电源和热传导的能量反馈是无关紧要的。虽然与星暴相关的超新星爆发可能会使星团内部10千秒差距的冷却延迟约18%，但它们无法将冷却气体维持在keV的温度。因此，A1068中的星星的形成似乎是由冷却的星团内介质提供燃料的。最后，我们提出的间接证据相反的观点，至少有一些，也许是所有的星星的形成可能是由cD和一个或多个同伴星系之间的相互作用。
In this paper and in a companion paper by Wise, McNamara, & Murray, we present a detailed, multiwavelength study of the A1068 galaxy cluster, and we use this data to test cooling and energy feedback models of galaxy clusters. Near-ultraviolet and infrared images of the cluster show that the cD galaxy is experiencing star formation at a rate of ~20-70 M☉ yr-1 over the past ≲100 Myr. The dusty starburst is concentrated toward the nucleus of the cD galaxy and in filamentary structures projecting 60 kpc into its halo. The Chandra X-ray image presented in Wise, McNamara, & Murray reveals a steep temperature gradient that drops from roughly 4.8 keV beyond 120 kpc to roughly 2.3 keV in the inner 10 kpc of the galaxy, where the starburst peaks. Over 95% of the ultraviolet and Hα photons associated with the starburst are emerging from regions cloaked in keV gas with very short cooling times (~100 Myr), as would be expected from star formation fueled by cooling condensations in the intracluster medium. However, the Chandra spectrum is consistent with but does not require cooling at a rate of 114-145 M☉ yr-1, factors of several below the rates found with the ROSAT observatory. The local cooling rate in the vicinity of the central starburst is ≲40 M☉ yr-1, which is consistent with the star formation rate determined with U-band and infrared data. We consider energy feedback into the intracluster medium by the radio source, heat conduction, and supernova explosions associated with the starburst. We find that energy feedback from both the radio source and thermal conduction are inconsequential in A1068. Although supernova explosions associated with the starburst may be able to retard cooling in the inner 10 kpc of the cluster by ~18% or so, they are incapable of maintaining the cooling gas at keV temperatures. Therefore, it is plausible that the star formation in A1068 is being fueled by the cooling intracluster medium. Finally, we present circumstantial evidence for the contrary view that at least some and perhaps all of the star formation may have been fueled by an interaction between the cD and one or more companion galaxies.