Confrontation of top-hat spherical collapse against dark halos from cosmological N-body simulations
Confrontation of top-hat spherical collapse against dark halos from cosmological N-body simulations
复制标题
宇宙学 N 体模拟中顶帽球形塌陷与暗晕的对抗
DOI：
10.1093/pasj/psv122
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发表时间：
2016
影响因子：
2.3
通讯作者：
Yasushi Suto
中科院分区：
文献类型：
--
作者：
Daichi Suto;Tetsu Kitayama;Ken Osato;Shin Sasaki;Yasushi Suto
顶帽球面塌陷模型是描述宇宙结构非线性增长的最基本的分析框架之一。即使在当前精密宇宙学的时代，TSC也已经推动并广泛应用于各种研究。虽然有许多研究以统计的方式检验其与数值模拟的有效性，但很少有分析将TSC动力学在单个对象的基础上进行比较，这正是我们在本文中尝试的。根据传统的球面过密度的TSC判据，我们从一个宇宙N体模拟中提取了100个晕atz=0。然后，我们追溯到它们在早期时期的球状对应。就在晕的转折期之前，它们的动力学很好地被热释光近似，但它们的回转纪元被系统地延迟了，相对于光晕的预测，它们的活动半径平均大了∼20%。我们发现，这种系统偏差主要可以归因于暗物质密度分布的不均匀/不均匀和非零速度色散，而这两者在TSC中都被忽略了。尤其是暗物质晕由内向外的崩塌和穿壳，在产生显著的速度色散中起着重要的作用。本文还简要讨论了这一结果的意义。
The top-hat spherical collapse model (TSC) is one of the most fundamental analytical frameworks to describe the non-linear growth of cosmic structure. TSC has motivated, and been widely applied in, various investigations even in the current era of precision cosmology. While numerous studies exist to examine its validity against numerical simulations in a statistical fashion, there are few analyses which compare the TSC dynamics in an individual object-wise basis, which is what we attempt in the present paper. We extract 100 halos atz= 0 from a cosmologicalN-body simulation according to the conventional TSC criterion for the spherical over-density. Then we trace back their spherical counterparts at earlier epochs. Just prior to the turn-around epoch of the halos, their dynamics are well approximated by TSC, but their turn-around epochs are systematically delayed and thevirialradii are larger by ∼20% on average relative to the TSC predictions. We find that this systematic deviation can mainly be ascribed to the non-uniformity/inhomogeneity of dark matter density profiles and the non-zero velocity dispersions, both of which are neglected in TSC. In particular, the inside-out collapse and shell-crossing of dark matter halos play an important role in generating the significant velocity dispersion. The implications of the present result are briefly discussed.