# LoCuSS: Testing hydrostatic equilibrium in galaxy clusters

Smith, GP, Mazzotta, P, Okabe, N, Ziparo, F, Mulroy, SL, Babul, A, Finoguenov, A, McCarthy, IG, Lieu, M, Bahe, Y, Bourdin, H, Evrard, AE, Futamase, T, Haines, CP, Jauzac, M, Marrone, DP, Martino, R, May, PE, Taylor, JE and Umetsu, K (2015) LoCuSS: Testing hydrostatic equilibrium in galaxy clusters. Monthly Notices of the Royal Astronomical Society, 456 (1). L74-L75. ISSN 0035-8711

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 $\beta_{\rm X}=0.95\pm0.05$, and for the 44 clusters also detected by Planck, the mean ratio of Planck mass estimate to LoCuSS lensing mass is $\beta_{\rm P}=0.95\pm0.04$. 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 $\beta_{\rm P}\simeq0.9-0.95$ at $0.15<z<0.3$. This small level of hydrostatic bias disagrees at $\sim5\sigma$ with the level required to reconcile Planck cosmology results from the cosmic microwave background and galaxy cluster counts.