The Cosmogrid Simulation: Statistical Properties of Small Dark Matter Halos (2048-650)

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 650 of the 2048³ resolution collection.

我们展示了基于一致性Λ冷暗物质（LCDM）模型的“宇宙网格（Cosmogrid）”宇宙学N体模拟套件的研究结果。本次Cosmogrid模拟在尺寸为30百万秒差距（Mpc）的立方模拟盒中开展，共采用2048³个粒子，每个粒子的质量为1.28×10^5 Msun（太阳质量），足以分辨超暗矮星系。研究发现，晕质量函数在低至~10^7 Msun的质量范围内与Sheth-Tormen拟合函数吻合良好。我们对三个星系群量级的大质量晕的球平均密度轮廓进行了分析，这三个晕均包含至少1.7亿个粒子，其密度轮廓的斜率在最内侧半径处变得比-1更为平缓。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通过单一幂律进行描述，但基于Navarro等人提出的Press-Schechter理论构建的简单模型，与该依赖性表现出良好的吻合度。自旋参数与晕质量未表现出显著相关性。对于质量大于~10^8 Msun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。次晕丰度与晕质量密切相关：星系量级的晕所拥有的次晕数量比~10^11 Msun的晕多出50%。本数据集为2048³分辨率模拟集合的第650号模拟快照。