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arXiv 2103.06505astro-ph.GAastro-ph.COastro-ph.HE
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椭圆星系团和星系团中活动星系核驱动外流的质量负荷

On the Mass Loading of AGN-Driven Outflows in Elliptical Galaxies and Clusters

Yu Qiu, Brian R. McNamara, Tamara Bogdanovic, Kohei Inayoshi, Luis C. Ho

摘要:

活动星系核(AGN)驱动的外流是吸积超大质量黑洞(SMBH)与宿主星系和星系团相互作用的重要通道。然而,由于缺乏热等离子体的动力学解析数据,渗透到环银河系和集群内空间的外流的属性约束不佳。在这项工作中,我们使用一个单一的参数,流出吸积质量加载因子$m=\dot{M}_{\rm out}/\dot{M}_{\rm BH}$,来表征的流出,介导SMBHs和他们的主机之间的相互作用。通过模拟M87和英仙座,并将模拟的热剖面与这两个系统的X射线观测结果进行比较,我们证明了$m$可以被限制在$200-500$之间。该参数对应于在大约1 kpc的$4,000-7,000\,{\rm km\,s}^{-1}$之间的总体流动速度和在$10^{8.7}-10^{9}\,{\rm K}$之间的热化流出温度。我们的研究结果表明,在巨大的椭圆星系和星系团的主导外流速度远低于在SMBH附近,信号的有效耦合和减速的周围介质的长度尺度低于1千秒差距。因此,活动星系核可能有效地发射出比先前通过测量冷的、模糊的物质发现的质量大$\sim10$倍的外流。我们还研究了冷气体的质量和速度分布,最终形成一个旋转支撑的磁盘在模拟集群。这种盘在观测中的罕见性表明,需要进一步的研究来了解冷气体形成后的演变。

英文摘要:

Outflows driven by active galactic nuclei (AGN) are an important channel for accreting supermassive black holes (SMBHs) to interact with their host galaxies and clusters. Properties of the outflows are however poorly constrained due to the lack of kinetically resolved data of the hot plasma that permeates the circumgalactic and intracluster space. In this work, we use a single parameter, outflow-to-accretion mass-loading factor $m=\dot{M}_{\rm out}/\dot{M}_{\rm BH}$, to characterize the outflows that mediate the interaction between SMBHs and their hosts. By modeling both M87 and Perseus, and comparing the simulated thermal profiles with the X-ray observations of these two systems, we demonstrate that $m$ can be constrained between $200-500$. This parameter corresponds to a bulk flow speed between $4,000-7,000\,{\rm km\,s}^{-1}$ at around 1 kpc, and a thermalized outflow temperature between $10^{8.7}-10^{9}\,{\rm K}$. Our results indicate that the dominant outflow speeds in giant elliptical galaxies and clusters are much lower than in the close vicinity of the SMBH, signaling an efficient coupling with and deceleration by the surrounding medium on length scales below 1 kpc. Consequently, AGNs may be efficient at launching outflows $\sim10$ times more massive than previously uncovered by measurements of cold, obscuring material. We also examine the mass and velocity distribution of the cold gas, which ultimately forms a rotationally supported disk in simulated clusters. The rarity of such disks in observations indicates that further investigations are needed to understand the evolution of the cold gas after it forms.

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