arXiv 1801.042822018-01astro-ph.GAastro-ph.HE

冷核星团：BCG的作用、恒星形成和活动星系核驱动的Turbulence

Cool-Core Clusters : Role of BCG, Star Formation & AGN-Driven Turbulence

Deovrat Prasad, Prateek Sharma, Arif Babul

备注：: Submitted to ApJ; Suggestions and comments are welcome; Substantially updated from the previous version; Abstract abridged; 12 pages, 11 figures
DOI：: 10.3847/1538-4357/aacce8

摘要：

最近的分析表明，它是重要的，明确包括中央最亮的中央星系（BCG）的引力势，以推断重力加速度（$g$）和自由落体时间（$t_{\rm ff} \equiv [2r/g]^{1/2}$）在冷的集群核心。精确测量$t_{\rm ff}$是至关重要的，因为根据数值模拟，冷气体冷凝和强反馈发生在最小值（$t_{\rm cool}/t_{\rm ff}$）低于接近10的阈值的簇芯中。最近的观察，包括BCG重力表明，所观察到的阈值min（$t_{\rm cool}/t_{\rm ff}$）位于略高的值，接近10-30;只有少数几个集群中，该比率远低于10。在本文中，我们比较了反馈AGN（活动星系核）喷流与团内介质（ICM）相互作用的数值模拟，有和没有BCG潜力。我们发现，对于一个固定的反馈效率，BCG的存在并不显着影响温度，但平均增加（减少）的核心密度（熵）。最重要的是，min（$t_{\rm cool}/t_{\rm ff}$）仅轻微地受BCG重力的影响。还值得注意的是，NFW+BCG运行中的最小值（$t_{\rm cool}/t_{\rm ff}$）比NFW运行中的最小值大约两倍。我们还研究了由于恒星形成而导致的冷气体耗尽的作用，并表明它只影响旋转主导分量（环面），而径向主导分量（调节反馈周期）基本上不受影响。在我们的模拟中，AGN喷流产生的金属粒子主要沿喷流方向分布，金属粒子的径向扩散较小，冷核团中的湍流较弱，这与Hitomi最近对英仙座星系团的研究结果一致。

英文摘要：

Recent analysis shows that it is important to explicitly include the gravitational potential of the central brightest central galaxy (BCG) to infer the acceleration due to gravity ($g$) and the free-fall time ($t_{\rm ff} \equiv [2r/g]^{1/2}$) in cool cluster cores. Accurately measuring $t_{\rm ff}$ is crucial because according to numerical simulations cold gas condensation and strong feedback occur in cluster cores with min($t_{\rm cool}/t_{\rm ff}$) below a threshold value close to 10. Recent observations which include the BCG gravity show that the observed threshold in min($t_{\rm cool}/t_{\rm ff}$) lies at a somewhat higher value, close to 10-30; there are only a few clusters in which this ratio falls much below 10. In this paper we compare numerical simulations of feedback AGN (Active Galactic Nuclei) jets interacting with the intracluster medium (ICM), with and without a BCG potential. We find that, for a fixed feedback efficiency, the presence of a BCG does not significantly affect the temperature but increases (decreases) the core density (entropy) on average. Most importantly, min($t_{\rm cool}/t_{\rm ff}$) is only affected slightly by the inclusion of the BCG gravity. Also notable is that the lowest value of min($t_{\rm cool}/t_{\rm ff}$) in the NFW+BCG runs are about twice larger than in the NFW runs. We also look at the role of depletion of cold gas due to star formation and show that it only affects the rotationally dominant component (torus), while the radially dominant component (which regulates the feedback cycle) remains largely unaffected. The distribution of metals due to AGN jets in our simulations is predominantly along the jet direction and the radial spread of metals is less. We also show that the turbulence in cool core clusters is weak, consistent with recent Hitomi results on Perseus cluster.

机构、总结、中文摘要均由AI分析而来，可能存在错误，请以论文正文为准。

摘要：

英文摘要：

相关论文