星系团核心气体运动的物理起源：对英仙座星系团Hitomi观测的解释
Physical Origins of Gas Motions in Galaxy Cluster Cores: Interpreting Hitomi Observations of the Perseus Cluster
摘要：
Hitomi X射线卫星提供了对星系团中等离子体速度分散的首次直接测量。它发现了一种相对“静止”的气体，其视线速度色散约为160 km/s，距离星团中心30 kpc至60 kpc。这是令人惊讶的，因为喷流和X射线空洞的存在表明正在进行的活动和来自星团中心活动星系核（AGN）的反馈。使用一组模拟瞳观测产生的一套国家的最先进的宇宙学集群模拟，和一个孤立的，但更高分辨率的模拟气体物理在集群核心，包括冷却和AGN反馈的影响，我们研究瞳检测到集群的可能性与观察到的速度。只要英仙座在过去的几十亿年里没有经历过一次大的合并，活动星系核的反馈也在以一种“温和”的模式运行，我们就可以重现瞳观察到的气体运动水平。频繁的机械AGN反馈产生净视线速度分散约100-200公里/秒，包括在英仙座核心测量的值。另一方面，在核心观测到的大尺度速度切变主要是由宇宙吸积（如合并）产生的。我们讨论了这些结果的影响活动星系核反馈物理和集群宇宙学和进展，需要在模拟和观测，包括瞳重新飞行和基于量热计的仪器具有更高的空间分辨率。
英文摘要：
The Hitomi X-ray satellite has provided the first direct measurements of the plasma velocity dispersion in a galaxy cluster. It finds a relatively "quiescent" gas with a line-of-sight velocity dispersion ~ 160 km/s, at 30 kpc to 60 kpc from the cluster center. This is surprising given the presence of jets and X-ray cavities that indicates on-going activity and feedback from the active galactic nucleus (AGN) at the cluster center. Using a set of mock Hitomi observations generated from a suite of state-of-the-art cosmological cluster simulations, and an isolated but higher resolution simulation of gas physics in the cluster core, including the effects of cooling and AGN feedback, we examine the likelihood of Hitomi detecting a cluster with the observed velocities. As long as the Perseus has not experienced a major merger in the last few gigayears, and AGN feedback is operating in a "gentle" mode, we reproduce the level of gas motions observed by Hitomi. The frequent mechanical AGN feedback generates net line-of-sight velocity dispersions ~100-200 km/s, bracketing the values measured in the Perseus core. The large-scale velocity shear observed across the core, on the other hand, is generated mainly by cosmic accretion such as mergers. We discuss the implications of these results for AGN feedback physics and cluster cosmology and progress that needs to be made in both simulations and observations, including a Hitomi re-flight and calorimeter-based instruments with higher spatial resolution.
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