Line-of-Sight Gas Sloshing in the Cool Core of Abell 907
Line-of-Sight Gas Sloshing in the Cool Core of Abell 907
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DOI：
10.3847/1538-4357/aafa19
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发表时间：
2018-12
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影响因子：
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通讯作者：
S. Ueda;Y. Ichinohe;T. Kitayama;K. Umetsu
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作者：
S. Ueda;Y. Ichinohe;T. Kitayama;K. Umetsu
我们目前的视线（LOS）气体晃动首次发现在一个冷的核心星系团。星系团阿贝尔907被确定为一个松弛的集群，由于它的全球X射线表面亮度所采取的钱德拉X射线天文台。然而，在去除团内介质（ICM）的全局发射之后的X射线剩余图像显示出在团核心中的弧形正过剩和围绕中心正过剩的负过剩，这反过来表明ICM的扰动。通过对这两个区域的X射线能谱分析，发现：（1）正过剩区的ICM温度和金属丰度分别低于和高于负过剩区;（2）ICM接近于压力平衡。我们还发现，在正的和负的过量之间有一个轻微的红移差，对应于km s−1（1σ）的速度切变。的X射线残留图像和ICM属性是一致的LOS气体晃动的预期。假设气体沿LOS相互沿着反向平行移动，则剪切速度预计为10800 km s-1。这一层的速度场能够提供非热压力支持，比热压力支持高出约34%。从剪切速度推断的总动能相当于晃动ICM的热光度的30%。因此，阿贝尔907是对气体晃动发生在天空平面的星系团的补充，对于理解晃动驱动的气体动力学及其对加热的影响以防止失控冷却是重要的。
We present line-of-sight (LOS) gas sloshing first found in a cool core in a galaxy cluster. The galaxy cluster Abell 907 is identified as a relaxed cluster owing to its global X-ray surface brightness taken by the Chandra X-ray Observatory. The X-ray residual image after removing the global emission of the intracluster medium (ICM), however, shows an arc-like positive excess and a negative excess surrounding the central positive excess in the cluster core, which in turn indicates a disturbance of the ICM. We analyze the X-ray spectra extracted from both regions and find that (1) the ICM temperature and the metal abundance in the positive excess are lower and higher than those in the negative excess, respectively, and (2) the ICM is nearly in pressure equilibrium. We also find a slight redshift difference between the positive and the negative excesses, which corresponds to the velocity shear of km s−1 (1σ). The X-ray residual image and the ICM properties are consistent with those expected by LOS gas sloshing. Assuming that the gas is moving inverse-parallel to each other along the LOS, the shear velocity is expected to be ∼800 km s−1. The velocity field of this level is able to provide nonthermal pressure support by ∼34% relative to the thermal one. The total kinetic energy inferred from the shear velocity corresponds to ∼30% of the bolometric luminosity of the sloshing ICM. Abell 907 is therefore complementary to galaxy clusters in which gas sloshing takes place in the plane of the sky, and is important for understanding gas dynamics driven by sloshing and its influence on the heating to prevent runaway cooling.