Study of the evolution of dense stellar systems by large-scale simulations on special-purpose computers

本研究的目的是澄清致密恒星系统，如球状星团，所谓的年轻和紧凑的集群，和星系核的动力学演化，通过直接N体模拟。研究的重点是大质量黑洞如何在这些系统的中心生长。具体来说，我们设定了两个目标。(a)确定合并不稳定性发生的判据，在合并不稳定性中，大质量恒星与其他大质量恒星逐渐合并形成超大质量恒星;（B）识别球状星团和其他大质量星星团中大质量中心黑洞的可观测特征。关于合并不稳定性的条件，我们发现，合并不稳定性的条件是大质量恒星的初始动力学摩擦时标较短（小于3 Mys），且初始核半径相当小。当以King模式安装时，W 0必须为8或更大。对于中心黑洞的观测特征，以前的观测研究寻找斜率为-7/4的尖点，从简单的单组分模型预测。通过考虑恒星演化和恒星质量函数的N体计算，我们发现带有中心大质量黑洞的球状星团的中心区域呈现出近似扁平的核。

The purpose of this study is to clarify the dynamical evolution of dense stellar systems, such as globular clusters, so-called young and compact clusters, and galactic nuclei, by means of direct N-body simulations. The focus of the study is how the massive black holes grow at the center of these systems. Specifically, we placed two goals. (a) To determine the criterion for the occurrence of the merging instability, in which massive stars merge with other massive stars progressively to form supermassive stars, and (b) to identify the observable signature of massive central black holes in globular clusters and other massive star clusters. As for the condition for the merging instability, we found that the condition is that the initial dynamical friction timescale of massive stars is short (less than 3Mys) and that the initial core radius is fairly small. When fitted by a King mode, W0 must be 8 or larger. For the observational signature of the central black hole, previous observational studies looked for a cusp with slope -7/4, predicted from simple single-component model. By means of N-body calculation in which stellar evolution and stellar mass function are taken into account, we found that the central region of a globular cluster with central massive black hole appears as almost flat core.