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arXiv 0911.4484astro-ph.CO
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没有比家更好的地方了Milky Way质量暗物质晕的统计

There's no place like home? Statistics of Milky Way-mass dark matter halos

Michael Boylan-Kolchin, Volker Springel, Simon D. M. White, Adrian Jenkins

摘要:

我们提出了一个银河系质量晕的结构特性的分布在千禧年-II模拟(MS-II)的分析。这个在标准LCDM宇宙学中的结构形成模拟包含数千个银河系质量的晕,并且具有足够的分辨率来正确地解决每个主机的许多subhalos。因此,它提供了一个重大的改进,在统计权力可用于探索分布的内部结构晕这种质量。此外,MS-II包含较低分辨率版本的Aquarius项目晕,使我们能够将我们的结果与高得多的分辨率下的六个晕的模拟结果进行比较。我们研究的质量大会的历史,subhalo质量函数和吸积时间,并合并和剥离的历史能够影响磁盘的中心晕subhalos的分布。我们发现,subhalo丰度是没有很好地描述泊松统计在低质量,而是由内在的散射为主。根据下沉时暗晕的质量和丰度匹配的假设,一个M_vir =10^12 M_sun的银河系晕拥有两个像麦哲伦云一样明亮的星系的可能性不到10%。对于M_vir=2.5 x 10^12 M_sun的晕,这种概率上升到25%。与磁盘加热相关的统计数据对被认为相关的质量范围非常敏感。合并时的质量:大于1:30的红移零维里质量很可能会撞击中央星系盘,这几乎是不可避免的,因为z=2,而在同一时期,只有一半的晕与落入质量:红移零维里质量大于1:10合并。

英文摘要:

We present an analysis of the distribution of structural properties for Milky Way-mass halos in the Millennium-II Simulation (MS-II). This simulation of structure formation within the standard LCDM cosmology contains thousands of Milky Way-mass halos and has sufficient resolution to properly resolve many subhalos per host. It thus provides a major improvement in the statistical power available to explore the distribution of internal structure for halos of this mass. In addition, the MS-II contains lower resolution versions of the Aquarius Project halos, allowing us to compare our results to simulations of six halos at a much higher resolution. We study the distributions of mass assembly histories, of subhalo mass functions and accretion times, and of merger and stripping histories for subhalos capable of impacting disks at the centers of halos. We show that subhalo abundances are not well-described by Poisson statistics at low mass, but rather are dominated by intrinsic scatter. Using the masses of subhalos at infall and the abundance-matching assumption, there is less than a 10% chance that a Milky Way halo with M_vir =10^12 M_sun will host two galaxies as bright as the Magellanic Clouds. This probability rises to ~25% for a halo with M_vir=2.5 x 10^12 M_sun. The statistics relevant for disk heating are very sensitive to the mass range that is considered relevant. Mergers with infall mass : redshift zero virial mass greater than 1:30 could well impact a central galactic disk and are a near inevitability since z=2, whereas only half of all halos have had a merger with infall mass : redshift zero virial mass greater than 1:10 over this same period.

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