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arXiv 0909.1318astro-ph.GAastro-ph.CO
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银河系中心的恒星分布和恒星剩余物

The Distribution of Stars and Stellar Remnants at the Galactic Center

David Merritt

备注：
ApJ, accepted
发表信息：
Astrophys.J.718:739-761,2010
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摘要：

最近的观测表明，银河系超大质量黑洞周围的老恒星密度低，核星团的模型被认为还没有达到一个稳定的状态下的引力相遇的影响。初始半径为1-1.5 pc的核心在10 Gyr之后演化为大约0.5 pc的大小，大致上是观测到的核心的大小。巴赫-沃尔夫尖点的缺失在这些模型中得到了自然的解释，而不需要微调或难以置信的初始条件。在没有尖点的情况下，一个10个太阳质量的黑洞从5 pc的初始距离螺旋进入银河系中心的时间可能远大于10 Gyr。假设恒星黑洞最初具有与恒星相同的相空间分布，那么在5-10 Gyr之后，它们的密度预计会急剧上升，进入恒星核心，但可能会大大低于从稳态模型推断的密度，其中包括恒星中的陡峭密度尖点。产生秒差距尺度初始核心的可能机制包括：在一个预先存在的三轴核中，在向心轨道上的恒星被摧毁，在超大质量黑洞附近的恒星形成被抑制，或者大质量双星的恒星被抛射。这些模型的影响进行了讨论的引力波inspiral事件的速率，以及其他物理过程，依赖于一个高密度的恒星或恒星质量的黑洞附近的人马座A*。

英文摘要：

Motivated by recent observations that suggest a low density of old stars around the Milky Way supermassive black hole, models for the nuclear star cluster are considered that have not yet reached a steady state under the influence of gravitational encounters. A core of initial radius 1-1.5 pc evolves to a size of approximately 0.5 pc after 10 Gyr, roughly the size of the observed core. The absence of a Bahcall-Wolf cusp is naturally explained in these models, without the need for fine-tuning or implausible initial conditions. In the absence of a cusp, the time for a 10-solar-mass black hole to spiral in to the Galactic center from an initial distance of 5 pc can be much greater than 10 Gyr. Assuming that the stellar black holes had the same phase-space distribution initially as the stars, their density after 5-10 Gyr is predicted to rise very steeply going into the stellar core, but could remain substantially below the densities inferred from steady-state models that include a steep density cusp in the stars. Possible mechanisms for the creation of the parsec-scale initial core include destruction of stars on centrophilic orbits in a pre-existing triaxial nucleus, inhibited star formation near the supermassive black hole, or ejection of stars by a massive binary. The implications of these models are discussed for the rates of gravitational-wave inspiral events, as well as other physical processes that depend on a high density of stars or stellar mass black holes near Sagittarius A*.

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