Cosmological simulations of black hole growth II: how (in)significant are merger events for fuelling nuclear activity?
Cosmological simulations of black hole growth II: how (in)significant are merger events for fuelling nuclear activity?
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DOI：
10.1093/mnras/sty2288
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发表时间：
2018-05
影响因子：
4.8
通讯作者：
L. Steinborn;M. Hirschmann;K. Dolag;F. Shankar;S. Juneau;M. Krumpe;R. Remus;Adelheid F. Teklu
中科院分区：
文献类型：
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作者：
L. Steinborn;M. Hirschmann;K. Dolag;F. Shankar;S. Juneau;M. Krumpe;R. Remus;Adelheid F. Teklu
究竟是什么机制在驱动星系中心的核活动，这是一个尚未解决的重大问题。在这项研究中，我们调查的统计相关性星系合并燃料气体到中央的几个千秒差距的星系，可能导致活动星系核（AGN）。为了有力地解决这一问题，我们采用了大规模的宇宙学流体动力学模拟从Magneticum Pathfinder集，包括黑洞吸积和AGN反馈模型。我们的模拟预测，对于z = 2的明亮活动星系核（LAGN > 1045 erg s（-1）），超过50%的宿主星系在过去的0.5 Gyr中经历了合并。然而，这些高合并分数，只是反映了内在的高合并分数的大质量星系在z = 2，其中发光活动星系核优先发生。除此之外，我们的模拟表明，合并事件不是统计上占主导地位的燃料机制的核活动在红移范围z = 0-2：不考虑aGNluminosity，不到20%的活动星系核主机平均经历了最近的合并，与一些观测研究。引发活动星系核活动所需的中央星际介质条件可能是，但不一定是由合并引起的。尽管合并在统计上的相关性很小，但在给定的活动星系核光度和恒星质量下，活动星系核宿主的合并分数可以比不活跃星系的合并分数高出三倍。这种升高的合并分数仍然指向活动星系核和合并之间的内在联系，与我们的传统预期一致。
Which mechanism(s) are mainly driving nuclear activity in the centres of galaxies is a major unsettled question. In this study, we investigate the statistical relevance of galaxy mergers for fuelling gas onto the central few kpc of a galaxy, potentially resulting in an active galactic nucleus (AGN). To robustly address that, we employ large-scale cosmological hydrodynamic simulations from the Magneticum Pathfinder set, including models for black hole accretion and AGN feedback. Our simulations predict that for luminous AGN (LAGN > 1045 erg s(-1)) at z = 2, more than 50 per cent of their host galaxies have experienced a merger in the last 0.5 Gyr. These high merger fractions, however, merely reflect the intrinsically high merger fractions of massive galaxies at z = 2, in which luminous AGN preferentially occur. Apart from that, our simulations suggest that merger events are not the statistically dominant fuelling mechanism for nuclear activity over a redshift range z = 0-2: irrespective ofAGNluminosity, less than 20 per cent of AGN hosts have on average undergone a recent merger, in agreement with a number of observational studies. The central interstellar medium conditions required for inducing AGN activity can be, but are not necessarily caused by a merger. Despite the statistically minor relevance of mergers, at a given AGN luminosity and stellar mass, the merger fractions of AGN hosts can be by up to three times higher than that of inactive galaxies. Such elevated merger fractions still point towards an intrinsic connection between AGN and mergers, consistent with our traditional expectation.