The Cosmogrid Simulation: Statistical Properties of Small Dark Matter Halos 2048³ resolution

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 30Mpc box with 2048³ particles. The mass of each particle is 1.28 x 10^5 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 collection contains the 2048³ resolution snapshots.

我们展示了基于一致性Λ冷暗物质（LCDM）模型的“Cosmogrid”宇宙学N体模拟套件的研究成果。该Cosmogrid模拟在边长为30百万秒差距（Mpc）的立方盒中完成，采用2048³个粒子进行计算，单个粒子的质量为1.28×10^5太阳质量（Msun），该分辨率足以解析超暗矮星系。我们发现，晕质量函数在低至约10^7太阳质量的范围内，与Sheth与Tormen拟合函数吻合度良好。我们还对三个质量最大的星系群级晕的球对称平均密度剖面展开了分析，这三个晕均包含至少1.7亿个粒子。这些密度剖面的斜率在最内侧半径处变得比-1更为平缓。此外，我们发现晕浓度与质量存在显著的相关性：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高。自旋参数与晕质量则未表现出相关性。对于质量大于约10^8太阳质量的晕，其浓度与自旋的概率分布函数均可通过对数正态分布（log-normal distribution）得到良好拟合。次晕丰度依赖于晕质量：星系级晕的次晕数量比约10^11太阳质量的晕多出50%。
本数据集集合包含2048³分辨率的快照文件。