星团、自相互作用暗物质晕和黑洞尖点：流体传导模型及其对广义相对论的扩展
Star Clusters, Self-Interacting Dark Matter Halos and Black Hole Cusps: The Fluid Conduction Model and its Extension to General Relativity
摘要：
采用流体传导近似研究球状星团和自相互作用暗物质（SIDM）晕的演化。我们还探讨了密度尖点的形成和动力学的影响，在这两个系统中出现由于存在一个巨大的，中央黑洞。我们处理的大N体，自引力系统是“弱碰撞”：恒星或SIDM粒子碰撞之间的平均自由时间比它们的特征交叉（动力学）时间尺度长得多，但比系统寿命短。流体传导模型可靠地跟踪了星团和SIDM晕中的“重力热灾难”，而没有黑洞。对于一个中心有大质量黑洞的星团，这种近似再现了与黑洞结合的恒星的Bahcall-Wolf准静态密度尖点，并显示了尖点如何阻止“重力热灾难”并导致星团重新膨胀。初始黑洞中心密度尖峰与外部NFW轮廓匹配的SIDM晕弛豫为具有由SIDM相互作用截面的速度依赖性确定的中心密度尖点的核心晕结构。流体传导方法在发展这种“弱碰撞”、准平衡牛顿系统方面的成功和相对简单，促使其扩展到相对论系统。我们在这里提出一个广义相对论的扩展。
英文摘要：
We adopt the fluid conduction approximation to study the evolution of spherical star clusters and self-interacting dark matter (SIDM) halos. We also explore the formation and dynamical impact of density cusps that arise in both systems due to the presence of a massive, central black hole. The large N-body, self-gravitating systems we treat are "weakly-collisional": the mean free time between star or SIDM particle collisions is much longer than their characteristic crossing (dynamical) time scale, but shorter than the system lifetime. The fluid conduction model reliably tracks the "gravothermal catastrophe" in star clusters and SIDM halos without black holes. For a star cluster with a massive, central black hole, this approximation reproduces the familiar Bahcall-Wolf quasistatic density cusp for the stars bound to the black hole and shows how the cusp halts the "gravothermal catastrophe" and causes the cluster to re-expand. An SIDM halo with an initial black hole central density spike that matches onto to an exterior NFW profile relaxes to a core-halo structure with a central density cusp determined by the velocity dependence of the SIDM interaction cross section. The success and relative simplicity of the fluid conduction approach in evolving such "weakly-collisional", quasiequilibrium Newtonian systems motivates its extension to relativistic systems. We present a general relativistic extension here.
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