Weak Lensing Analysis of CODEX Clusters using Dark Energy Camera Legacy Survey : Mass-Richness Relation

TL;DR

This study uses weak lensing data from the DECam Legacy Survey to analyze the mass-richness relation of 279 CODEX galaxy clusters, confirming a power-law relation and consistency with dynamical mass estimates.

Contribution

It provides the first weak lensing-based measurement of the mass-richness relation for CODEX clusters using DECaLS data, validating previous dynamical mass estimates.

Findings

Mass-richness relation follows a power law with index ~1.

Weak lensing and dynamical mass estimates are in excellent agreement.

Cluster mass estimates are robust across different richness groups.

Abstract

We present the weak lensing analysis of 279 CODEX clusters using imaging data from 4200 $\text{deg}^{2}$ of the DECam Legacy Survey (DECaLS) Data Release 3. The cluster sample results from a joint selection in X-ray, optical richness in the range $20 \leq \lambda < 110$, and redshift in the range $0.1 \leq z \leq 0.2$. We model the cluster mass ($M_{\rm 200c}$) and the richness relation with the expression $\left\langle M_{\rm 200c} | \lambda \right\rangle \propto M_{0} \, (\lambda / 40)^{F_{\lambda}}$. By measuring the CODEX cluster sample as an individual cluster, we obtain the best-fit values, $M_{0} = 3.24^{+0.29}_{-0.27} \times 10^{14} \text{M}_{\odot}$, and $F_{\lambda} = 1.00 ^{+0.22}_{-0.22}$ for the richness scaling index, consistent with a power law relation. Moreover, we separate the cluster sample into three richness groups; $\lambda = 20 - 30, 30 - 50$ and $50 - 110$, and measure the stacked excess surface mass density profile in each group. The results show that both methods are consistent. In addition, we find an excellent agreement between our weak lensing based scaling relation and the relation obtained with dynamical masses estimated from cluster member velocity dispersions measured by the SDSS-IV/SPIDERS team. This suggests that the cluster dynamical equilibrium assumption involved in the dynamical mass estimates is statistically robust for a large sample of clusters.