The Spatial Distribution of Satellite Galaxies Selected from Redshift Space

TL;DR

This study analyzes the spatial distribution of satellite galaxies using mock redshift surveys from simulations, revealing differences based on host galaxy color and mass, and fitting the distribution with NFW and power-law profiles.

Contribution

It introduces a methodology for analyzing satellite distributions in mock redshift surveys and compares the spatial profiles for red and blue host galaxies across different masses.

Findings

Satellite distributions fit well with NFW and power-law profiles.

Red host satellites have larger scale parameters than blue host satellites.

Satellite distribution around blue hosts is more concentrated than their halos.

Abstract

We investigate the spatial distribution of satellite galaxies using a mock redshift survey of the first Millennium Run simulation. The satellites were identified using common redshift space criteria and the sample therefore includes a large percentage of interlopers. The satellite locations are well-fitted by a combination of a Navarro, Frenk & White(NFW) density profile and a power law. At fixed stellar mass, the NFW scale parameter, r_s, for the satellite distribution of red hosts exceeds r_s for the satellite distribution of blue hosts. In both cases the dependence of r_s on host stellar mass is well-fitted by a power law. For the satellites of red hosts, r_s^{red} \propto (M_\ast / M_\sun)^{0.71 \pm 0.05} while for the satellites of blue hosts, r_s^{blue} \propto (M_\ast / M_\sun)^{0.48 \pm 0.07}$. For hosts with stellar masses greater than 4.0E+10 M_sun, the satellite distribution around blue hosts is more concentrated than is the satellite distribution around red hosts. The spatial distribution of the satellites of red hosts traces that of the hosts' halos; however, the spatial distribution of the satellites of blue hosts is more concentrated than that of the hosts' halos by a factor of ~2. Our methodology is general and applies to any analysis of satellites in a mock redshift survey. However, our conclusions necessarily depend upon the semi-analytic galaxy formation model that was adopted, and different galaxy formation models may yield different results.