## Abstract

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

Original language | English |
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Pages (from-to) | 3341-3354 |

Number of pages | 14 |

Journal | Monthly Notices of the Royal Astronomical Society |

Volume | 490 |

Issue number | 3 |

DOIs | |

Publication status | Published - 1 Dec 2019 |

## Keywords

- Galaxies: clusters: general
- X-rays: galaxies: clusters