Joint Analysis of Cluster Observations: II. Chandra/XMM-Newton X-ray and Weak Lensing Scaling Relations for a Sample of 50 Rich Clusters of Galaxies

TL;DR

This study analyzes X-ray and weak lensing data for 50 galaxy clusters, finding gas mass as the most reliable mass estimator with low scatter, and revealing biases in hydrostatic mass estimates especially for non-cool-core clusters.

Contribution

It provides a comprehensive multiwavelength analysis of cluster scaling relations, highlighting the robustness of gas mass as a mass proxy and quantifying biases in hydrostatic mass estimates.

Findings

Gas mass shows 15% intrinsic scatter as a mass proxy.

Hydrostatic masses underestimate weak lensing masses by 10% on average.

Cool-core clusters exhibit no significant bias in mass estimates.

Abstract

We present a study of multiwavelength X-ray and weak lensing scaling relations for a sample of 50 clusters of galaxies. Our analysis combines Chandra and XMM-Newton data using an energy-dependent cross-calibration. After considering a number of scaling relations, we find that gas mass is the most robust estimator of weak lensing mass, yielding 15 +/- 6% intrinsic scatter at r500 (the pseudo-pressure YX has a consistent scatter of 22%+/-5%). The scatter does not change when measured within a fixed physical radius of 1 Mpc. Clusters with small BCG to X-ray peak offsets constitute a very regular population whose members have the same gas mass fractions and whose even smaller <10% deviations from regularity can be ascribed to line of sight geometrical effects alone. Cool-core clusters, while a somewhat different population, also show the same (<10%) scatter in the gas mass-lensing mass relation. There is a good correlation and a hint of bimodality in the plane defined by BCG offset and central entropy (or central cooling time). The pseudo-pressure YX does not discriminate between the more relaxed and less relaxed populations, making it perhaps the more even-handed mass proxy for surveys. Overall, hydrostatic masses underestimate weak lensing masses by 10% on the average at r500; but cool-core clusters are consistent with no bias, while non-cool-core clusters have a large and constant 15-20% bias between r2500 and r500, in agreement with N-body simulations incorporating unthermalized gas. For non-cool-core clusters, the bias correlates well with BCG ellipticity. We also examine centroid shift variance and and power ratios to quantify substructure; these quantities do not correlate with residuals in the scaling relations. Individual clusters have for the most part forgotten the source of their departures from self-similarity.