Luminous Red Galaxy Population in Clusters at $0.2\le z\le 0.6$

TL;DR

This study analyzes the distribution and properties of luminous red galaxies (LRGs) in galaxy clusters at redshifts 0.2 to 0.6, revealing their halo occupation, Poisson nature, and radial profiles, informing galaxy evolution models.

Contribution

It provides the first detailed characterization of LRG halo occupation and radial distribution within clusters at intermediate redshift, using photometric redshifts and specific color criteria.

Findings

LRG halo occupation follows a power-law with specific parameters.

Both LRGs and satellite LRGs exhibit Poisson distribution characteristics.

LRGs' radial profile fits an NFW profile with a measured concentration.

Abstract

We investigate statistical properties of LRGs in a sample of X-ray selected galaxy clusters at intermediate redshift ($0.2\le z\le0.6$). The LRGs are selected based on carefully designed color criteria, and the cluster membership is assessed via photometric redshifts. As clusters and LRGs are both viewed as promising tracer of the underlying dark matter distribution, understanding the distribution of LRGs within clusters is an important issue. Our main findings include: 1. The halo occupation distribution of LRGs inside our cluster sample is $N(M) = k\times (M/10^{14})^{a}$ where $a=0.620\pm 0.105 $ and $k=1.425\pm0.285 $ assuming a Poisson distribution for $N(M)$. 2. The halo occupation distribution of LRGs ($N(M)$) and the satellite distribution of LRGs ($N-1(M)$) are both consistent with being Poisson. To be more quantitative, we find $Var(N)/<N>= 1.428\pm 0.351$ and $Var(N-1)/<N-1> = 1.823 \pm 0.496$ 3. The radial profile of LRGs within clusters when fitted with a NFW profile gives a concentration of $17.5^{+7.1}_{-4.3}$ ($6.0^{+3.2}_{-1.9}$) including (excluding) BLRGs (Brightest LRGs). We also discuss the implications of these observations on the evolution of massive galaxies in clusters.