Fluctuations in finite-N equilibrium stellar systems
Fluctuations in finite-N equilibrium stellar systems
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有限 N 平衡恒星系统中的涨落
DOI：
10.1046/j.1365-8711.1998.01456.x
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发表时间：
1997
影响因子：
4.8
通讯作者：
M. Weinberg
中科院分区：
文献类型：
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作者：
M. Weinberg
在大尺度下，恒星系统中泊松噪声的引力放大是很重要的。例如，对于King模型轮廓，它将偶极噪声功率增加了大约六倍，将四极噪声增加了50%。对于无磁芯的Hernquist模型，偶极子噪声被放大了15倍。这些预言是用Rostoker & Rosenbluth（1960）的缀饰粒子形式计算的，并通过n体模拟得到证实。这一结果意味着无碰撞的n体模拟是不可能的;引起弛豫的涨落噪声是自引力的固有部分。换句话说，消除两体松弛并不能完全消除松弛。应用于暗物质晕的盘星系，粒子数至少为10 - 6将是必要的，以抑制这种噪音在一个水平，不占主导地位或显着影响磁盘的响应。相反，晕圈很可能远离相位混合平衡，由此产生的噪声频谱可能会引发或激发观察到的结构，如扭曲，螺旋臂和酒吧。例如，在晕中的离散噪声，类似于由于人口10 6 M的黑洞可以产生可观察到的翘曲，并可能激发或种子其他磁盘结构。
Gravitational amplification of Poisson noise in stellar systems is important on large scales. For example, it increases the dipole noise power by roughly a factor of six and the quadrupole noise by 50% for a King model profile. The dipole noise is amplified by a factor of fifteen for the core-free Hernquist model. The predictions are computed using the dressed-particle formalism of Rostoker & Rosenbluth (1960) and are demonstrated by n-body simulation. This result implies that a collisionless n-body simulation is impossible; The fluctuation noise which causes relaxation is an intrinic part of self gravity. In other words, eliminating two-body relaxation does not eliminate relaxation altogether. Applied to dark matter halos of disk galaxies, particle numbers of at least 10 6 will be necessary to suppress this noise at a level that does not dominate or significantly affect the disk response. Conversely, halos are most likely far from phase-mixed equilibrium and the resulting noise spectrum may seed or excite observed structure such as warps, spiral arms and bars. For example, discreteness noise in the halo, similar to that due to a population of 10 6 M⊙ black holes can produce observable warping and possibly excite or seed other disk structure.