Comparing with redshift surveys of galaxies

Redshift surveys –brief review CFA galaxies (1983) Las Campanas galaxies (1996) 2dF ,000 galaxies (2003) SDSS ,000 galaxies (2008?)

The role of different observations

Clustering and environment analysis The key is to account for the incompleteness correctly For example, two-point correlation function is measured very simply with DD(r)/RR(r)- 1, where DD and RR are the number of pairs of galaxies in the observed sample and in the random sample respectively; The key is to construct the random sample correctly

Incompleteness or selection effects Magnitude limited sample----radial selection effect; Limiting magnitude variation (0.1 typically) across the survey region; Survey boundary; Redshift measurement completeness; –Sampling rate; –Magnitude dependent redshift incompleteness –Fiber collision

Random sample A sample of the points randomly distributed spatially but with the same observational selection effects

光度函数： – 单位体积、单位光度间隔内 的星系平均数目 –Schechter function: 两点相关函数： – 与均匀随机场相比，在距离 某个星系 r 处发现另一个星 系的额外几率 相对速度弥散： 背 景 介 绍背 景 介 绍 统计量

红移空间畸变： 本征运动使星系看起来偏离膨胀背景 红移空间 2PCF ： 沿视向，大尺度压扁，小尺度拉伸 背 景 介 绍背 景 介 绍 测量方法

背 景 介 绍背 景 介 绍

Redshift two-point correlation functions for DR2 (Li, C. et al. astroph/ ; ; see also Zehavi et al. 2005)

Dependence of CF on physical properties (Li et al. 2005a,b)

Luminosity dependence of the bias (r_p=2.7 Mpc/h; Zehavi et al. 2005) Stellar mass dependence (Li, et al 2005a,b) 星系成团的幅度，即 偏袒因子 b ，随光度 （上图）和恒星质量 （下图）的变化。

Velocity dispersion vs. physical properties (Li, C. et al. 2005b)

Velocity vs luminosity (Li, et al. 2005a,b)

Bimodal distribution in the color- magnitude diagram (SDSS)

Three ways of interpreting Halo Occupation Distribution (HOD) model (e.g. Jing et al. 1998; Yang et al 2003) Using galaxy formation models –Hydro/N-body simulations with star formation (physical processes; id of galaxies? e.g. V. Springel et al. 2005)Hydro/N-body simulations –Semi-analytical models of galaxy formation + N-body simulations (e.g. Kauffmann et al. 1999)

Physical processes of galaxy formation Formation of dark halos; gas shock heated; Gas cooled radiatively; Stars formed from cold gas; Massive stars short lived; form neutron stars and supernova explosions Explosions inject energy and metals into interstellar medium (hot+cold); heating and enrich---feedback effects Mergers of galaxies after their host halos merge; Black hole formation and its AGN feedback

Dark matter Galaxies: red for E; blue for spirals

理 论 比 较理 论 比 较 构建 SDSS 的模拟样本 SDSS DR4  L500 L100+L300

Agreement after the reduction of faint satellites

Subhalo resolved: the bimodal color-mag distribution is much better reproduced

Summary Main features of galaxies can be explained in current galaxy formation models; High precision modeling for galaxy formation is still challenging, for very complicated physical process