Cosmological Simulations of Formation of Galaxies and Clustersand Origin of biasing

(1)暗物质晕和高密度峰中的非线性随机偏倚：我们使用宇宙学n体模拟量化了偏倚物体聚类的非线性和随机性程度。采用波峰和晕作为偏置模型的代表，重点研究了偏置物体与暗物质的两点相关及其相互关系。特别地，我们考虑了红移空间畸变的影响，并试图通过分析偏置因子和互相关因子来澄清尺度依赖性和时间依赖性。在小尺度上，随机性和非线性变得明显，并且强烈依赖于物体，特别是在红移空间中，由于有偏的物体的成对速度色散。然而，确定性线性偏置的近似即使在准线性状态下也能很好地工作，线性红移空间畸变解释了这种状态下红移空间中的聚类幅度。(2)基于宇宙流体力学模拟的星系和星系团的偏态模型：利用宇宙流体力学模拟对空间平坦的低密度COM宇宙中星系和暗晕的非线性和随机偏态进行了广泛的分析。我们将它们的偏置特性与解析晕偏置模型的预测结果进行了比较。有趣的是，通过外推晕偏倚模型的预测，可以更好地描述星系的偏倚特性。在之前的模拟中，星系的星团振幅几乎与z=0和3之间的红移无关。我们还发现星系的偏差与它们的形成时代有明显的关系；年老星系群的分布与潜在的质量密度场密切相关，而年轻星系群的分布相对于暗物质来说更具随机性和反偏性。老年人口两点相关函数的振幅约为年轻人口两点相关函数的3倍。此外，年老的星系群存在于大质量的暗晕中，而年轻的星系则优先形成于较小的暗晕中。假设观测到的早型和晚型星系分别对应于模拟的老星系群和年轻星系群，所有这些星系的分离都与观测到的早型和晚型星系的分离一致，如星系的形态-密度关系。少

(1) Nonlinear Stochastic Biasing in dark matter halos and high-density peaks : We quantifiesthe degree of nonlinearity and stochasticity of the clustering of biased objects, using cosmological N-body simulations. Adopting the peaks and the halos as representative biasing models, we focus on the two-point correlation of the biased objects, dark matter and their cross-correlation. Especially, we take account of the effect of redshift-space distortion and attempt to clarify the scale-dependence and the time-dependence by analyzing the biasing factor and the cross-correlation factor. On small scales, stochasticity and nonlinearity become appreciable and strongly object-dependent, especially in redshift space due to the pair-wise velocity dispersion of the biased objects. Nevertheless, an approximation of deterministic linear biasingworks reasonably well even in the quasi-linear regime, and linear redshift-space distortion explains the clustering amplitudes in redshift space in this regime. … More (2) Biasing model of galaxies and clusters on the basis of cosmological hydrodynamic simulations :We perform an extensive analysis of nonlinear and stochastic biasing of galaxies and dark halos in spatially flat low-density COM universe using cosmological hydrodynamic simulations. We compare their biasing properties with the predictions of an analytic halo biasing model. Interestingly the biasing properties of galaxies are better described by extrapolating the halo biasing model predictions. The clustering amplitudes of galaxies are almost independent of the redshift between z=0 and 3 as reported in previous simulations. We also find the clear dependence of galaxy biasing on their formation epoch ; the distribution of old populations of galaxies tightly correlates with the underlying mass density field, while that of young populations is slightly more stochastic and anti-biased relative to dark matter. The amplitude of two-point correlation function of old populations is about 3 times larger than that of the young populations. Furthermore, the old population of galaxies reside within massive dark halos while the young galaxies are preferentially formed in smaller dark halos. Assuming that the observed early and late-type galaxies correspond to the simulated old and young populations of galaxies, respectively, all of these segregations of galaxies are consistent with observational ones for the early and late-type of galaxies such as the morphology-density relation of galaxies. Less