Halo Occupation Distribution Modeling of Clustering of Luminous Red Galaxies

TL;DR

This study uses Halo Occupation Distribution modeling to analyze the clustering of luminous red galaxies in SDSS, revealing their halo environments, luminosity-halo mass relations, and implications for galaxy formation and cosmology.

Contribution

It provides detailed HOD parameters for luminous red galaxies, linking their clustering to halo properties and offering insights into galaxy evolution models.

Findings

Most LRGs are central galaxies in massive halos.

Satellite LRGs are a small percentage, influencing small-scale clustering.

Luminosity of central LRGs scales with halo mass as Lc ∝ M^0.5.

Abstract

We perform Halo Occupation Distribution (HOD) modeling to interpret small-scale and intermediate-scale clustering of 35,000 luminous early-type galaxies and their cross-correlation with a reference imaging sample of normal L* galaxies in the Sloan Digital Sky Survey. The modeling results show that most of these luminous red galaxies (LRGs) are central galaxies residing in massive halos of typical mass M ~ a few times 10^13 to 10^14 Msun/h, while a few percent of them have to be satellites within halos in order to produce the strong auto-correlations exhibited on smaller scales. The mean luminosity Lc of central LRGs increases with the host halo mass, with a rough scaling relation of Lc \propto M^0.5. The halo mass required to host on average one satellite LRG above a luminosity threshold is found to be about 10 times higher than that required to host a central LRG above the same threshold. We find that in massive halos the distribution of L* galaxies roughly follows that of the dark matter and their mean occupation number scales with halo mass as M^1.5. The HOD modeling results also allows for an intuitive understanding of the scale-dependent luminosity dependence of the cross-correlation between LRGs and L_* galaxies. Constraints on the LRG HOD provide tests to models of formation and evolution of massive galaxies, and they are also useful for cosmological parameter investigations. In one of the appendices, we provide LRG HOD parameters with dependence on cosmology inferred from modeling the two-point auto-correlation functions of LRGs.