Galaxy Evolution from Halo Occupation Distribution Modeling of Deep2 and Sdss Galaxy Clustering

We model the luminosity-dependent projected two-point correlation function of DEEP2 and SDSS galaxies within the Halo Occupation Distribution (HOD) framework. From this we infer the relationship between galaxy luminosity and host dark matter halo mass at z ∼ 1 and at z ∼ 0. At both epochs, there is a tight correlation between central galaxy luminosity and halo mass, with the slope and scatter decreasing for larger halo masses, and the fraction of satellite galaxies decreasing at higher luminosity. Central L∗ galaxies reside in halos a few times more massive at z ∼ 1 than at z ∼ 0. The satellite fraction of galaxies more luminous than L∗ is ∼10% at z ∼ 1, compared to ∼20% at z ∼ 0. We find little evolution in the relation between the characteristic minimum mass of a halo hosting a central galaxy above a luminosity threshold and the mass scale of a halo that on average hosts one satellite galaxy above the same luminosity threshold, with the latter being 15–20 times the former. Combining these HOD results with theoretical predictions of the typical growth of halos, we establish an evolutionary connection between the galaxy populations at the two redshifts by linking z ∼ 0 central galaxies to z ∼ 1 central galaxies that reside in their progenitor halos, which enables us to study the evolution of galaxies as a function of halo mass. We find that the stellar mass growth of galaxies depends on halo mass. On average, the majority of the stellar mass in central galaxies residing in z ∼ 0 low mass halos (∼ 5× 10hM⊙) is the result of star formation between z ∼ 1 and z ∼ 0, while only a small fraction of the stellar mass in central galaxies of high mass halos (∼ 10hM⊙) is the result of star formation over this period. In addition, the mass scale of halos where the star formation efficiency reaches a maximum is found to shift toward lower mass with time. Future work that combines HOD modeling of the clustering of appropriately defined galaxy samples at different redshifts with the assembly history and dynamical evolution of dark matter halos can lead to an understanding of the stellar mass growth due to both mergers and star formation as a function of host halo mass and provide powerful tests of galaxy formation theories. In the appendix, we provide a brief discussion of systematic biases related to the assumption of “one galaxy per halo” in estimating the mass scale and number density of host halos from the observed clustering strength of galaxies. Subject headings: cosmology: observations — galaxies: clustering — galaxies: distances and redshifts — galaxies: evolution — galaxies: halos — galaxies: statistics — large-scale structure of universe