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

Abstract

We introduce a galaxy cluster mass observable, μ*, based on the stellar masses of cluster members, and we present results for the Dark Energy Survey (DES) Year 1 (Y1) 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 μ* works as a promising mass proxy by comparing our predictions to X-ray measurements. We measure the X-ray temperature–μ* relation for a total of 129 clusters matched between the wide-field DES Y1 redMaPPer catalogue and Chandra and XMM archival observations, spanning the redshift range 0.1 < z < 0.7. For a scaling relation that is linear in logarithmic space, we find a slope of α = 0.488 ± 0.043 and a scatter in the X-ray temperature at fixed μ* of σlnTX|μ* = 0.266+−00019020 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 μ*-conditioned scatter in mass, finding σlnM|μ* = 0.26+−001510. These results are competitive with well-established cluster mass proxies used for cosmological analyses, showing that μ* can be used as a reliable and physically motivated mass proxy to derive cosmological constraints.