Spatial Correlation Function and Pairwise Velocity Dispersion of Galaxies: Cold Dark Matter Models versus the Las Campanas Survey
Spatial Correlation Function and Pairwise Velocity Dispersion of Galaxies: Cold Dark Matter Models versus the Las Campanas Survey
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DOI：
10.1086/305209
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发表时间：
1997-07
期刊：
影响因子：
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通讯作者：
Y. Jing;Y. Jing;H. Mo;G. Börner
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文献类型：
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作者：
Y. Jing;Y. Jing;H. Mo;G. Börner
我们表明，大N体模拟的帮助下，无论是真实空间的两点相关函数和成对的星系速度色散可以可靠地测量从拉斯坎帕纳斯红移调查。实空间相关函数符合幂律r（r）=（r 0/r）γ，其中r 0 =（5.06 ± 0.12）h-1 Mpc，γ = 1.862 ± 0.034，在1 h-1 Mpc时两两速度频散为570 ± 80 km s-1。这些观测结果和当前冷暗物质（CDM）宇宙演化的预测进行了详细的比较。我们从大量的高分辨率N体模拟中为每个理论模型构建了60个模拟样本，这使我们能够在分析中包括各种观测选择效应，并对真实的和理论样本使用完全相同的方法。我们证明，这样的程序是必不可少的模型和观测之间的比较。观测到的两点相关函数是显着平坦的质量相关函数在目前的CDM模型上的尺度为1h-1 Mpc。观测到的成对速度色散也低于这些模型中的暗物质粒子。我们提出了一个简单的反偏见模型来解释这些差异。这个模型假设每单位暗物质质量的星系数N/M随暗晕质量的增加而减少。当N/M随M的变化趋势处于已观测到的富星系团水平时，σ8 Ω0.60~0.4-0.5和Γ 0.2的CDM模型的预测与观测结果是一致的。因此，用Γ ~ 0.2和星系团丰度归一化的CDM模型与观测到的星系相关函数和两两速度色散是一致的。在这些模型中不需要高水平的速度偏差。
We show, with the help of large N-body simulations, that both the real-space two-point correlation function and pairwise velocity dispersion of galaxies can be measured reliably from the Las Campanas Redshift Survey. The real-space correlation function is well fitted by the power law ξ(r) = (r0/r)γ with r0 = (5.06 ± 0.12) h-1 Mpc and γ = 1.862 ± 0.034, and the pairwise velocity dispersion at 1 h-1 Mpc is 570 ± 80 km s-1. A detailed comparison between these observational results and the predictions of current cold dark matter (CDM) cosmogonies is carried out. We construct 60 mock samples for each theoretical model from a large set of high-resolution N-body simulations, which allows us to include various observational selection effects in the analyses and to use exactly the same methods for both real and theoretical samples. We demonstrate that such a procedure is essential in the comparison between models and observations. The observed two-point correlation function is significantly flatter than the mass correlation function in current CDM models on scales ≲1 h-1 Mpc. The observed pairwise velocity dispersion is also lower than that of dark matter particles in these models. We propose a simple antibias model to explain these discrepancies. This model assumes that the number of galaxies per unit dark matter mass, N/M, decreases with the mass of dark haloes. The predictions of CDM models with σ8 Ω0.60~0.4-0.5 and Γ ~ 0.2 are in agreement with the observational results, if the trend of N/M with M is at the level already observed for rich clusters of galaxies. Thus CDM models with Γ ~ 0.2 and with cluster-abundance normalization are consistent with the observed correlation function and pairwise velocity dispersion of galaxies. A high level of velocity bias is not required in these models.