The galactic center massive black hole and nuclear star cluster
The galactic center massive black hole and nuclear star cluster
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DOI：
10.1103/revmodphys.82.3121
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发表时间：
2010-06
影响因子：
44.1
通讯作者：
R. Genzel;F. Eisenhauer;S. Gillessen
中科院分区：
文献类型：
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作者：
R. Genzel;F. Eisenhauer;S. Gillessen
银河系中心是一个研究可能发生在许多其他星系核的现象和物理过程的绝佳实验室。我们银河系的中心是迄今为止距离我们最近的星系核，其观测的分辨率和灵敏度达到了电磁辐射能量的18个数量级。理论模拟在解释这些测量方面变得越来越强大。本文综述了中央秒差距的观测和理论研究的最新进展，重点介绍了中央大质量黑洞的实验证据和周围致密核星星团的过程。通过对20多颗恒星的轨道分析以及对中央致密射电源Sgr A* 的大小和运动的测量，我们提出了目前的证据，即这个射电源必须是一个大约4.4 × 1e6 Msun的大质量黑洞，毫无疑问。我们报告了围绕这个黑洞的致密核星星团的结构和演化，包括最近在Sgr A* 附近形成的恒星的惊人事实，显然具有头重脚轻的恒星质量函数。我们讨论了一个密集的浓度较暗的恒星集中在附近的大质量黑洞，其中三个轨道peribothroi小于一个光天。这个“S星团”似乎主要由年轻的早期型恒星组成，与黑洞周围平衡的“恒星尖点”的预测性质相反。这构成了一个值得注意的、目前尚未完全理解的“青年悖论”。我们还总结了什么是已知的吸积气体到Sgr A* 的发射特性，以及如何这种发射开始描绘在热吸积区的事件视界周围的物理性质。
The Galactic Center is an excellent laboratory for studying phenomena and physical processes that may be occurring in many other galactic nuclei. The Center of our Milky Way is by far the closest galactic nucleus, and observations with exquisite resolution and sensitivity cover 18 orders of magnitude in energy of electromagnetic radiation. Theoretical simulations have become increasingly more powerful in explaining these measurements. This review summarizes the recent progress in observational and theoretical work on the central parsec, with a strong emphasis on the current empirical evidence for a central massive black hole and on the processes in the surrounding dense nuclear star cluster. We present the current evidence, from the analysis of the orbits of more than two dozen stars and from the measurements of the size and motion of the central compact radio source, Sgr A*, that this radio source must be a massive black hole of about 4.4 \times 1e6 Msun, beyond any reasonable doubt. We report what is known about the structure and evolution of the dense nuclear star cluster surrounding this black hole, including the astounding fact that stars have been forming in the vicinity of Sgr A* recently, apparently with a top-heavy stellar mass function. We discuss a dense concentration of fainter stars centered in the immediate vicinity of the massive black hole, three of which have orbital peri-bothroi of less than one light day. This 'S-star cluster' appears to consist mainly of young early-type stars, in contrast to the predicted properties of an equilibrium 'stellar cusp' around a black hole. This constitutes a remarkable and presently not fully understood 'paradox of youth'. We also summarize what is known about the emission properties of the accreting gas onto Sgr A* and how this emission is beginning to delineate the physical properties in the hot accretion zone around the event horizon.