On the formation of compact, massive subsystems in stellar clusters and its relation with intermediate-mass black holes
On the formation of compact, massive subsystems in stellar clusters and its relation with intermediate-mass black holes
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DOI：
10.1093/mnras/stv2265
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发表时间：
2015-02
影响因子：
4.8
通讯作者：
M. Arca-Sedda
中科院分区：
文献类型：
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作者：
M. Arca-Sedda
在它们的演化过程中，星团经历了质量隔离，最大质量恒星的轨道缩小，而较轻的恒星则从星团中心向外移动。在这种背景下，最近对几个星系和星系外球状星团（GCs）的观测和动力学模型表明，大多数球状星团在靠近其中心的地方显示出过多的质量，其性质仍有争议。例如，许多研究表明，轨道分离的恒星可能以失控的方式相互碰撞，导致形成非常大质量的恒星或中等质量黑洞（IMBH），其质量与观测到的质量过剩相当。另一方面，如果IMBH形成失败，分离的恒星可以形成一个致密的系统。在本文中，我们研究了致密，质量子系统（MSS）的早期形成阶段在几个gc模型中使用最近发展的半解析处理的质量偏析过程。为了研究MSS性质如何依赖于主簇性质，我们改变了模型的初始质量函数（IMF）、总质量、空间分布和金属丰度。我们的研究结果显示了IMF对MSS最终质量的影响，而金属丰度和空间分布只起次要作用。本文提出的方法使我们能够提供与观测到的相关性一致的连接MSS质量和主机集群质量的缩放关系。为了跟踪mss的早期形成阶段并改进我们的统计结果，我们对质量在$10^3$到$2 $ × 10^5$太阳质量之间的星团进行了几次$N$体模拟。
During their evolution, star clusters undergo mass segregation, by which the orbits of the most massive stars shrink, while the lighter stars move outwards from the cluster centre. In this context, recent observations and dynamical modelling of several galactic and extra-galactic globular clusters (GCs) suggest that most of them show, close to their centre, an overabundance of mass whose nature is still matter of debate. For instance, many works show that orbitally segregated stars may collide with each other in a runaway fashion, leading to the formation of a very massive star or an intermediate mass black hole (IMBH) with a mass comparable to the observed mass excess. On the other hand, segregated stars can form a dense system if the IMBH formation fails. In this paper we study the early formation phase of a dense, massive sub-system (MSS) in several GCs models using a recently developed semi-analytical treatment of the mass segregation process. In order to investigate how the MSS properties depend on the host cluster properties, we varied initial mass function (IMF), total mass, spatial distribution and metallicity of our models. Our results show how the IMF contributes to determine the final mass of the MSS, while the metallicity and the spatial distribution play a minor role. The method presented in this paper allowed us to provide scaling relations that connect the MSS mass and the host cluster mass in agreement with the observed correlation. In order to follow the early formation stage of the MSSs and improve our statistical results, we performed several $N$-body simulations of stellar clusters with masses between $10^3$ and $2\times 10^5$ solar masses.