Institute of Physics, Eötvös University, Pázmány P.s., Budapest, 1117, Hungary.
Phys Rev Lett. 2018 Sep 7;121(10):101101. doi: 10.1103/PhysRevLett.121.101101.
Gravitational torques among objects orbiting a supermassive black hole drive the rapid reorientation of orbital planes in nuclear star clusters (NSCs), a process known as vector resonant relaxation. In this Letter, we determine the statistical equilibrium of systems with a distribution of masses, semimajor axes, and eccentricities. We average the interaction over the apsidal precession time and construct a Monte Carlo Markov chain method to sample the microcanonical ensemble of the NSC. We examine the case of NSCs formed by 16 episodes of star formation or globular cluster infall. We find that the massive stars and stellar mass black holes form a warped disk, while low mass stars resemble a spherical distribution with a possible net rotation. This explains the origin of the clockwise disk in the Galactic center and predicts a population of black holes (BHs) embedded within this structure. The rate of mergers among massive stars, tidal disruption events of massive stars by BHs, and BH-BH mergers are highly increased in such disks. The first two may explain the origin of the observed G1 and G2 clouds, the latter may be important for gravitational wave detections with LIGO and VIRGO. More generally, black holes are expected to settle in disks in all dense spherical stellar systems assembled by mergers of smaller systems including globular clusters.
在绕超大质量黑洞运行的物体之间，引力扭矩会导致核星团（NSC）的轨道平面迅速重新定向，这一过程被称为向量共振弛豫。在这封信件中，我们确定了具有质量、半长轴和偏心率分布的系统的统计平衡。我们对进动时间进行平均，并构建了蒙特卡罗马尔可夫链方法来对 NSC 的微正则系综进行采样。我们研究了由 16 个恒星形成或球状星团内落事件形成的 NSC 的情况。我们发现，大质量恒星和恒星质量黑洞形成了一个翘曲盘，而低质量恒星则类似于具有可能的净旋转的球形分布。这解释了银河系中心顺时针盘的起源，并预测了这种结构中嵌入的黑洞（BH）的种群。在这样的盘中，大质量恒星之间的合并、大质量恒星被 BH 潮汐瓦解以及 BH-BH 合并的速率都大大增加。前两种可能解释了观察到的 G1 和 G2 云的起源，后一种可能对 LIGO 和 VIRGO 的引力波探测很重要。更一般地说，预计黑洞将在由较小系统（包括球状星团）合并形成的所有密集的球形恒星系统中 settle 在盘内。
