Dynamical evolution of black hole subsystems in idealized star clusters
Dynamical evolution of black hole subsystems in idealized star clusters
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DOI：
10.1093/mnras/stt628
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发表时间：
2013-04
影响因子：
4.8
通讯作者：
Philip G. Breen;D. Heggie
中科院分区：
文献类型：
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作者：
Philip G. Breen;D. Heggie
本文研究了含有恒星质量黑洞（BH）子系统的球状星星团。这是通过考虑两个组件模型来完成的，因为这些是更现实的多质量系统的最简单近似，其中一个组件代表BH人口，另一个代表所有其他恒星。这些系统被发现经历了一个漫长的演化阶段，系统的中心是由一个密集的BH子系统。质量分离后，大部分的BH驱动成一个紧凑的子系统，BH子系统的演化被发现的集群中包含的影响。BH子系统以满足整个集群的能源需求的方式发展，就像一个组件系统的核心必须满足整个集群的能源需求一样。BH子系统被发现存在了相当长的时间。从形成致密BH子系统到失去90%的子系统总质量（约为BH子系统形成时的半质量弛豫时间的10^{3}倍），大约需要10 t_{rh，i}，其中t_{rh，i}是初始半质量弛豫时间。根据理论计算，BH子系统的质量损失率（\dot{M}_2）为-（beta*zeta*M）/（alpha*t_{rh}），其中M为总质量，t_{rh}为半质量弛豫时间，alpha，beta，zeta为三个无量纲参数（详见第2节）。一个有趣的结果是BH子系统的质量损失率与恒星质量比（m_2/m_1）和总质量比（M_2/M_1）基本无关。（在m_2/m_1 >~ 10和M_2/M_1 ~ 10^{-2}的范围内，其中m_1，m_2分别为单个低质量和高质量粒子的质量，M_1，M_2为相应的总质量）。
In this paper, globular star clusters which contain a sub-system of stellar-mass black holes (BH) are investigated. This is done by considering two-component models, as these are the simplest approximation of more realistic multi-mass systems, where one component represents the BH population and the other represents all the other stars. These systems are found to undergo a long phase of evolution where the centre of the system is dominated by a dense BH sub-system. After mass segregation has driven most of the BH into a compact sub-system, the evolution of the BH sub-system is found to be influenced by the cluster in which it is contained. The BH sub-system evolves in such a way as to satisfy the energy demands of the whole cluster, just as the core of a one component system must satisfy the energy demands of the whole cluster. The BH sub-system is found to exist for a significant amount of time. It takes approximately 10t_{rh,i}, where t_{rh,i} is the initial half-mass relaxation time, from the formation of the compact BH sub-system up until the time when 90% of the sub-system total mass is lost (which is of order 10^{3} times the half-mass relaxation time of the BH sub-system at its time of formation). Based on theoretical arguments the rate of mass loss from the BH sub-system (\dot{M}_2) is predicted to be -(beta*zeta*M)/(alpha*t_{rh}), where M is the total mass, t_{rh} is the half-mass relaxation time, and alpha, beta, zeta are three dimensionless parameters (see Section 2 for details). An interesting consequence of this is that the rate of mass loss from the BH sub-system is approximately independent of the stellar mass ratio (m_2/m_1) and the total mass ratio (M_2/M_1) (in the range m_2/m_1 >~ 10 and M_2/M_1 ~ 10^{-2}, where m_1, m_2 are the masses of individual low-mass and high-mass particles respectively, and M_1, M_2 are the corresponding total masses).