The Cosmogrid Simulation: Statistical Properties of Small Dark Matter Halos (2048-549)

We present the results of the "Cosmogrid" cosmological N-body simulation suites based on the concordance LCDM model. The Cosmogrid simulation was performed in a 30 Mpc box with 2048³ particles. The mass of each particle is 1.28x10^5 Msun, which is sufficient to resolve ultra-faint dwarfs. We found that the halo mass function shows good agreement with the Sheth & Tormen fitting function down to ~10^7 Msun. We have analyzed the spherically averaged density profiles of the three most massive halos which are of galaxy group size and contain at least 170 million particles. The slopes of these density profiles become shallower than -1 at the inner most radius. We also find a clear correlation of halo concentration with mass. The mass dependence of the concentration parameter cannot be expressed by a single power law, however a simple model based on the Press-Schechter theory proposed by Navarro et al. gives reasonable agreement with this dependence. The spin parameter does not show a correlation with the halo mass. The probability distribution functions for both concentration and spin are well fitted by the log-normal distribution for halos with the masses larger than ~10^8 Msun. The subhalo abundance depends on the halo mass. Galaxy-sized halos have 50% more subhalos than ~10^11 Msun halos have. This is snapshot 549 of the 2048³ resolution collection.

本研究呈现基于一致性ΛCDM模型的‘Cosmogrid’宇宙学N体模拟套件的研究结果。该模拟在边长为30 Mpc（百万秒差距）的模拟盒子中开展，包含2048³个粒子，单个粒子质量为1.28×10^5 Msun（太阳质量），该分辨率足以分辨超暗矮星系。研究发现，晕质量函数在低至~10^7倍太阳质量的范围内，与Sheth-Tormen拟合函数吻合良好。我们分析了三个质量最大的星系群尺度晕的球平均密度剖面，每个晕至少包含1.7亿个粒子。这些密度剖面在最内侧半径处的斜率陡度小于-1。此外，我们发现晕浓度与晕质量存在显著相关性：浓度参数的质量依赖性无法用单一幂律描述，但基于Navarro等人提出的Press-Schechter理论的简单模型，与该依赖性的吻合度较为理想。自旋参数与晕质量未表现出相关性。对于质量大于~10^8倍太阳质量的晕，其浓度和自旋的概率分布函数均可通过对数正态分布得到良好拟合。次晕丰度依赖于晕质量：星系尺度的晕所含次晕数量比~10^11倍太阳质量的晕多50%。本数据集为2048³分辨率系列的第549个快照。