Stellar mass as a galaxy cluster mass proxy: application to the Dark Energy Survey redMaPPer clusters

Abstract

We introduce a galaxy cluster mass observable, $\hat{I}{¼}_{\star }$, based on the stellar masses of cluster members, and we present results for the Dark Energy Survey (DES) Year 1 observations. Stellar masses are computed using a Bayesian Model Averaging method, and are validated for DES data using simulations and COSMOS data. We show that $\hat{I}{¼}_{\star }$ works as a promising mass proxy by comparing our predictions to X-ray measurements. We measure the X-ray temperature-$\hat{I}{¼}_{\star }$ relation for a total of 150 clusters matched between the wide-field DES Year 1 redMaPPer catalogue, and Chandra and XMM archival observations, spanning the redshift range $0.1<z<0.7$. For a scaling relation which is linear in logarithmic space, we find a slope of $\hat{I}\pm =0.488\pm 0.043$ and a scatter in the X-ray temperature at fixed $\hat{I}{¼}_{\star }$ of $\ddot{I}{ƒ}_{\ln T_X|\hat{I}{¼}_{\star }}=0.266_{-0.020}^{+0.019}$ for the joint sample. By using the halo mass scaling relations of the X-ray temperature from the Weighing the Giants program, we further derive the $\hat{I}{¼}_{\star }$-conditioned scatter in mass, finding $\ddot{I}{ƒ}_{\ln M|\hat{I}{¼}_{\star }}=0.26_{-0.10}^{+0.15}$. These results are competitive with well-established cluster mass proxies used for cosmological analyses, showing that $\hat{I}{¼}_{\star }$ can be used as a reliable and physically motivated mass proxy to derive cosmological constraints.

14 pages, 7 figures, addressing MNRAS referee comments