N-body simulations of globular clusters in tidal fields: Effects of intermediate-mass black holes
N-body simulations of globular clusters in tidal fields: Effects of intermediate-mass black holes
复制标题
潮汐场中球状星团的 N 体模拟：中等质量黑洞的影响
DOI：
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发表时间：
2013
期刊：
影响因子：
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通讯作者：
J. Kruijssen
中科院分区：
文献类型：
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作者：
N. Lutzgendorf;H. Baumgardt;J. Kruijssen
上下文中等质量黑洞（IMBHs）可能提供了理解早期宇宙中超大质量黑洞生长的缺失环节。一些形成方案预测IMBH可能是由球状星团（GC）中的失控碰撞形成的。然而，在一个基本上没有气体（因此也没有吸积）的恒星系统（如GC）中，对黑洞的质量设置观测约束是具有挑战性的。了解GC中心的IMBH对其环境的影响可能会提供间接检测方法。目标。我们的目标是测试不同的初始组成的GC对它们在潮汐场中的演化的影响。我们确定了关键的观测值，表明在集群的中心存在一个IMBH。除了中央IMBHs，我们还考虑了不同的恒星质量黑洞保留和恒星二元分数的影响。方法.我们进行了一组22 N体模拟和不同的粒子数，IMBH质量，恒星质量黑洞保留分数，和恒星二元分数。这些模型都运行在一个外部的潮汐场，研究黑洞对集群的质量损失，质量函数和寿命的影响。最后，我们将我们的结果与观测数据进行了比较。结果我们发现，一个中心的大质量黑洞增加了高质量恒星从星星团的逃逸率，这意味着在低质量端的质量函数的相对耗尽进行得不那么快。此外，我们发现了一个类似的行为，一个集群托管大量的恒星质量黑洞，而不是一个巨大的中央IMBH。IMBH的存在也微弱地影响了由恒星残骸构成的星团质量的比例，就像原始双星的存在一样。我们将我们的模拟与文献中的观测数据进行了比较，发现我们的模型与观测到的GC的质量函数和结构参数之间有很好的一致性。我们利用这一协议，以确定GC可能潜在的主机IMBH。
Context. Intermediate-mass black holes (IMBHs) may provide the missing link to understanding the growth of supermassive black holes in the early Universe. Some formation scenarios predict that IMBHs could have formed by runaway collisions in globular clusters (GCs). However, it is challenging to set observational constraints on the mass of a black hole in a largely gas-free (and hence accretion-free) stellar system such as a GC. Understanding the influence of an IMBH in the center of a GC on its environment might provide indirect detection methods. Aims. Our goal is to test the effects of different initial compositions of GCs on their evolution in a tidal field. We pin down the crucial observables that indicate the presence of an IMBH at the center of the cluster. In addition to central IMBHs, we also consider the effects of different stellar-mass black hole retention and stellar binary fractions. Methods. We performed a set of 22 N-body simulations and varied particle numbers, IMBH masses, stellar-mass black-hole retention fractions, and stellar binary fractions. These models are all run in an external tidal field to study the effect of black holes on the cluster mass loss, mass function, and life times. Finally, we compared our results with observational data. Results. We found that a central massive black hole increases the escape rate of high-mass stars from a star cluster, implying that the relative depletion of the mass function at the low-mass end proceeds less rapidly. Furthermore, we found a similar behavior for a cluster hosting a high number of stellar-mass black holes instead of one massive central IMBH. The presence of an IMBH also weakly affects the fraction of the cluster mass that is constituted by stellar remnants, as does the presence of primordial binaries. We compared our simulations with observational data from the literature and found good agreement between our models and observed mass functions and structural parameters of GCs. We exploited this agreement to identify GCs that could potentially host IMBHs.