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Mass variance from archival X-ray properties of Dark Energy Survey Year-1 galaxy clusters Article uri icon


  • Farahi, A., Chen, X., Evrard, A. E., Hollowood, D. L., Wilkinson, R., Bhargava, S., Giles, P., Romer, A. K., Jeltema, T., Hilton, M., Bermeo, A., Mayers, J., Vergara Cervantes, C., Rozo, E., Rykoff, E. S., Collins, C., Costanzi, M., Everett, S., Liddle, A. R., Mann, R. G., Mantz, A., Rooney, P., Sahlen, M., Stott, J., Viana, P. T. P., et al


  • 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, ?RM, for clusters in the redshift range 0.2 , for clusters in the redshift range 0.2 , for clusters in the redshift range 0.2 X measurements are > 50{{ per cent}} complete for clusters with ?RM > 130. Regression analysis on the two samples produces consistent posterior scaling parameters, from which we derive a combined constraint on the residual scatter, s _{ln T | ? }= 0.275 ± 0.019. Joined with constraints for TX scaling with 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, s _{ln M | ? }= 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 the covariance of TX and ?RM at fixed mass, dominate the systematic error. The 95{{ per cent}} confidence region from joint sample analysis is relatively broad, s _{ln M | ? }\in [0.14, 0.55], or a factor 10 in variance.

publication date

  • 2019