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arXiv 1909.08280astro-ph.GA
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不等质量星系合并中潮汐破裂率演化的直接n体模拟

Direct n-body simulations of tidal disruption rate evolution in unequal-mass galaxy mergers

Shuo Li, Peter Berczik, Xian Chen, F. K. Liu, Rainer Spurzem, Yu Qiu

摘要:

分级星系形成模型预测了星系核中的超大质量黑洞双星。由于缺乏气体的环境和有限的观测空间分辨率,它们可能隐藏在许多星系的中心。然而,一颗恒星与其中一个超大质量黑洞(SMBH)的近距离相遇可能会使它发生潮汐破裂事件(TDE),并暂时照亮SMBH。在以前的工作中,我们研究了直接N-BODY模拟的TDE率的演变SMBHB系统在星系合并等质量。在这项工作中,我们扩展到不平等的质量合并。我们的研究结果表明,当两个SMBH彼此远离时,每个宿主星系的TDE率与孤立星系相似。随着两个星系和它们的SMBH分离的缩小,TDE速率逐渐增加,直到在两个SMBH结合后不久达到最大值。在这一阶段,平均TDE率可以提高几倍到一个数量级相对于孤立的单个星系。我们的模拟表明,TDE吸积率的依赖关系的质量比在这一阶段可以很好地拟合的幂律关系的两个SMBH。结合态SMBHB形成后,TDE速率随其进一步演化而降低。我们还发现,在次要合并TDE的次级SMBH期间和之后的绑定的二元形成主要是由来自其他星系的恒星。

英文摘要:

The hierarchical galaxy formation model predicts supermassive black hole binaries (SMBHBs) in galactic nuclei. Due to the gas poor environment and the limited spatial resolution in observations they may hide in the center of many a galaxy. However, a close encounter of a star with one of the supermassive black holes (SMBHs) may tidally disrupt it to produce a tidal disruption event (TDE) and temporarily light up the SMBH. In a previous work, we investigated with direct N-BODY simulations the evolution of TDE rates of SMBHB systems in galaxy mergers of equal mass. In this work we extend to unequal mass mergers. Our results show that, when two SMBHs are far away from each other, the TDE rate of each host galaxy is similar as in an isolated galaxy. As the two galaxies and their SMBHs separation shrinks, the TDE rate is increasing gradually until it reaches a maximum shortly after the two SMBHs become bound. In this stage, the averaged TDE rate can be enhanced by several times to an order of magnitude relative to isolated single galaxies. Our simulations show that the dependence of the TDE accretion rate on the mass ratio in this stage can be well fitted by power law relations for both SMBHs. After the bound SMBHB forms, the TDE rate decreases with its further evolution. We also find that in minor mergers TDEs of the secondary SMBH during and after the bound binary formation are mainly contributed by stars from the other galaxy.

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