LoCuSS: Testing hydrostatic equilibrium in galaxy clusters

Abstract

We test the assumption of hydrostatic equilibrium in an X-ray luminosity selected sample of 50 galaxy clusters at $0.15<z<0.3$ from the Local Cluster Substructure Survey (LoCuSS). Our weak-lensing measurements of $M_{500}$ control systematic biases to sub-4 per cent, and our hydrostatic measurements of the same achieve excellent agreement between XMM-Newton and Chandra. The mean ratio of X-ray to lensing mass for these 50 clusters is ${\hat{I}}_{\mathrm{X}}^2=0.95\pm 0.05$, and for the 44 clusters also detected by Planck, the mean ratio of Planck mass estimate to LoCuSS lensing mass is ${\hat{I}}_{\mathrm{P}}^2=0.95\pm 0.04$. Based on a careful like-for-like analysis, we find that LoCuSS, the Canadian Cluster Comparison Project (CCCP), and Weighing the Giants (WtG) agree on ${\hat{I}}_{\mathrm{P}}^2\simeq 0.9-0.95$ at $0.15<z<0.3$. This small level of hydrostatic bias disagrees at $\sim 5\ddot{I}ƒ$ with the level required to reconcile Planck cosmology results from the cosmic microwave background and galaxy cluster counts.

5 pages, 1 figure, accepted by MNRAS