大质量黑洞双星的长期演化。IV。具有碰撞弛豫核的星系合并
Long-term evolution of massive black hole binaries. IV. Mergers of galaxies with collisionally relaxed nuclei
摘要：
我们模拟星系之间的合并包含碰撞松弛核周围的大质量黑洞（MBH）。我们的星系包含四个质量群，代表古老的恒星星族;主要目标是了解合并后恒星质量黑洞（BH）的分布。合并之后使用直接求和N体模拟，假设质量比为1：3和两个不同的轨道。二进制MBH的演变，直到它的分离已经缩小了20倍以下的硬二进制分离。在星系合并的过程中，大的核心在恒星分布中被切割出来，半径是大质量双星影响半径的几倍。大部分预先存在的质量隔离在此阶段被消除。我们遵循的合并星系的演化约三个，中央弛豫时间合并后的大规模二元标准，头重脚轻，质量函数被认为是。在恒星分布中形成的核心仍然存在，恒星质量的黑洞的分布在这个基本上固定的背景下演化。即使在一个中心弛豫时间之后，这些模型看起来也与通常假设用于描述大质量BH附近恒星和恒星残骸分布的弛豫多质量模型非常不同。虽然恒星黑洞确实在大致的弛豫时间尺度上形成了一个尖点，但黑洞密度可能比那些模型小得多。我们讨论的影响，我们的研究结果的EMRI问题和Bahcall-Wolf尖点的存在。
英文摘要：
We simulate mergers between galaxies containing collisionally-relaxed nuclei around massive black holes (MBHs). Our galaxies contain four mass groups, representative of old stellar populations; a primary goal is to understand the distribution of stellar-mass black holes (BHs) after the merger. Mergers are followed using direct-summation N-body simulations, assuming a mass ratio of 1:3 and two different orbits. Evolution of the binary MBH is followed until its separation has shrunk by a factor of 20 below the hard-binary separation. During the galaxy merger, large cores are carved out in the stellar distribution, with radii several times the influence radius of the massive binary. Much of the pre-existing mass segregation is erased during this phase. We follow the evolution of the merged galaxies for approximately three, central relaxation times after coalescence of the massive binary; both standard, and top-heavy, mass functions are considered. The cores that were formed in the stellar distribution persist, and the distribution of the stellar-mass black holes evolves against this essentially fixed background. Even after one central relaxation time, these models look very different from the relaxed, multi-mass models that are often assumed to describe the distribution of stars and stellar remnants near a massive BH. While the stellar BHs do form a cusp on roughly a relaxation time-scale, the BH density can be much smaller than in those models. We discuss the implications of our results for the EMRI problem and for the existence of Bahcall-Wolf cusps.
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