LoCuSS: A Comparison of Cluster Mass Measurements from XMM-Newton and Subaru - Testing Deviation from Hydrostatic Equilibrium and Non-Thermal Pressure Support

TL;DR

This study compares X-ray hydrostatic and weak-lensing mass estimates for galaxy clusters, revealing small average discrepancies and trends related to cluster dynamical states, and confirms the reliability of combined XMM-Newton and Subaru observations.

Contribution

It provides a detailed comparison of mass measurement techniques using XMM-Newton and Subaru data, highlighting the effects of cluster disturbance on mass estimates and gas fractions.

Findings

Mass ratio close to unity for the whole sample (1-M^{X}/M^{WL}=0.01+/-0.07)

Better agreement in undisturbed clusters (1-M^{X}/M^{WL}=0.09+/-0.06)

Gas mass fractions increase with radius, independent of dynamical state

Abstract

We compare X-ray hydrostatic and weak-lensing mass estimates for a sample of 12 clusters that have been observed with both XMM-Newton and Subaru. At an over-density of \Delta=500, we obtain 1-M^{X}/M^{WL}=0.01+/-0.07 for the whole sample. We also divided the sample into undisturbed and disturbed sub-samples based on quantitative X-ray morphologies using asymmetry and fluctuation parameters, obtaining 1-M^{X}/M^{WL}=0.09+/-0.06 and -0.06+/-0.12 for the undisturbed and disturbed clusters, respectively. In addition to non-thermal pressure support, there may be a competing effect associated with adiabatic compression and/or shock heating which leads to overestimate of X-ray hydrostatic masses for disturbed clusters, for example, in the famous merging cluster A1914. Despite the modest statistical significance of the mass discrepancy, on average, in the undisturbed clusters, we detect a clear trend of improving agreement between M^{X} and M^{WL} as a function of increasing over-density, M^{X}/M^{WL}=(0.908+/-0.004)+(0.187+/-0.010) \log_{10}(\Delta /500). We also examine the gas mass fractions, f_{gas}=M^{gas}/M^{WL}, finding that they are an increasing function of cluster radius, with no dependence on dynamical state, in agreement with predictions from numerical simulations. Overall, our results demonstrate that XMM-Newton and Subaru are a powerful combination for calibrating systematic uncertainties in cluster mass measurements.