Statistics of N-Body Simulations - Part Two - Equal Masses after Core Collapse
Statistics of N-Body Simulations - Part Two - Equal Masses after Core Collapse
复制标题
N 体模拟统计 - 第二部分 - 核心塌陷后的等质量
DOI：
10.1093/mnras/270.2.298
复制
发表时间：
1994
期刊：
影响因子：
--
通讯作者：
D. Heggie
中科院分区：
文献类型：
--
作者：
M. Giersz;D. Heggie
本文介绍并分析了大量等质量孤立系统的 N 体模拟的统计结果，其中 250 ≤ N ≤ 2000。它集中于核心塌陷结束时开始的阶段。双星起着至关重要的作用，我们发现束缚对的总能量符合理论预期。由于硬/软阈值上存在多个二进制文件，总数的解释变得复杂。硬双星的相互作用与 Spitzer (1987) 的横截面一致。核心塌陷后半质量半径的空间演化几乎遵循经典理论，并且通过与福克-普朗克和气体模型进行比较，可以重新确定有效导热率和弛豫时间表达式中库仑对数的参数。如果通常假设的连续能量生产被随机能量生产模型所取代，则系统内部在核心弹跳时的演化与这些简化模型是一致的。类似地，核心塌陷后的演化需要对能量产生系数进行适度的重新校准，特别是对于小 N 而言。这些评论指的是许多模型的平均行为；个别病例表现出交替且不规则的扩张和再塌陷阶段。核心弹跳后不久，速度色散和各向异性的分布就变得非常同源。系统的束缚质量随时间的变化几乎遵循幂律。少数逃逸者（被认为是与二元活动相关的逃逸者）主导了被带走的能量：逃逸者的能量分布在核心崩溃结束时突然发生变化。逃逸双星的“内”能与理论预期一致，再次支持斯皮策硬双星的反应截面。
This paper presents and analyses statistical results from a large number of N -body simulations of isolated systems with equal masses, in which 250 ≤ N ≤ 2000. It concen-trates on the phase starting around the end of core collapse. Binaries play a crucial role, and we find that the total energy of bound pairs is in line with theoretical expectations. Interpretation of the total number is complicated by the presence of a number of binaries on the hard/soft threshold. Interactions of hard binaries are consistent with the Spitzer (1987) cross section. The spatial evolution of the half-mass radius after core collapse nearly follows classical theory, and, by comparison with Fokker-Planck and gas models, allows a redetermination of the effective thermal conductivity and the argument of the Coulomb logarithm in the expression for the relaxation time. The evolution of the inner parts of the system around the time of core bounce is consistent with these simplified models provided that the continuous production of energy, as usually assumed, is replaced by a model of stochastic energy production. Similarly, post-collapse evolution of the core requires a modest recalibration of the coefficient of energy generation, especially for small N . These remarks refer to the behaviour averaged over many models; individual cases show alternate and irregular phases of expansion and recollapse. The distributions of velocity dispersion and anisotropy become remarkably homologous soon after core bounce. The bound mass of the systems very nearly follows a power law with time. A small number of escapers, presumed to be those associated with binary activity, dominate the energy which is carried off: the distribution of energies of escapers changes abruptly at the end of core collapse. The “internal” energy of escaping binaries is consistent with theoretical expectations, and again supports Spitzer’s reaction cross section for hard binaries.