暗物质晕普适性的数值分析

N体数值模拟计算发现暗物质晕具有几乎普适的密度轮廓,比如NFW轮廓、Moore轮廓和Einasto轮廓等,而速度各向异性和密度轮廓的对数斜率近似成线性关系.同样有证据显示赝相空间密度ρ/σ3与半径r成幂律关系.本文从金斯方程的角度出发通过自洽性研究考察了这几种常用密度轮廓的鲁棒性问题.数值计算和分析比较的结果表明各向异性密度轮廓并不具有鲁棒性,进而可以推测暗物质晕的这一数值特性缺乏真正的普适性.

Numerical Analysis on Universal Properties of Dark Matter Halos

N-body simulations show that dark matter halos have a nearly universal density profile such as NFW profile, Moore profile and Einasto profile. The velocity anisotropy and the logarithmic slope of the density profile seem to have a linear relation. The simulations also show that the so-called ＂pseudo phase-space density＂ p/o＂3 behaves as a power-law in radius r. We study the issue of the robustness of those universal properties with Jeans equation and find that the velocity anisotropy profile seems to be sensitive to other numerical aspects and therefore not universal in essence.