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要旨:
Using archival X-ray observations and a lognormal population model, we estimate constraints on the intrinsic scatter in halo mass at fixed optical richness for a galaxy cluster sample identified in Dark Energy Survey Year-One (DES-Y1) data with the redMaPPer algorithm. We examine the scaling behaviour of X-ray temperatures, TX, with optical richness, λRM, for clusters in the redshift range 0.2 < z < 0.7. X-ray temperatures are obtained from Chandra and XMM observations for 58 and 110 redMaPPer systems, respectively. Despite non-uniform sky coverage, the TX measurements are >50 per cent complete for clusters with λRM on the two samples produces consistent posterior scaling parameters, from which we derive a combined constraint on the residual scatter, σlnT|λ=0.275±0.019. Joined with constraints for TX halo mass from the Weighing the Giants program and richness–temperature covariance estimates from the LoCuSS sample, we derive the richness-conditioned scatter in mass, σlnM|λ=0.30±0.04(stat)±0.09(sys) at an optical richness of approximately 100. Uncertainties in external parameters, particularly the slope and variance of the TX–mass relation and , scaling with > 130. Regression analysis the covariance of TX and λRM at fixed mass, dominate the systematic error. The 95 per cent confidence region from joint sample analysis is relatively broad, σlnM|λ∈[0.14,0.55], or a factor 10 in variance.
