2016MNRAS.461.4182M

We compare X-ray and caustic mass profiles for a sample of 16 massive galaxy clusters. We assume hydrostatic equilibrium in interpreting the X-ray data, and use large samples of cluster members with redshifts as a basis for applying the caustic technique. The hydrostatic and caustic masses agree to better than ≃20 per cent on average across the radial range covered by both techniques (∼[0.2-1.25]R₅₀₀). The mass profiles were measured independently and do not assume a common functional form. Previous studies suggest that, at R₅₀₀, the hydrostatic and caustic masses are biased low and high, respectively. We find that the ratio of hydrostatic to caustic mass at R₅₀₀ is 1.20^{+0.13}_{-0.11}; thus it is larger than 0.9 at ≃3σ and the combination of under- and overestimation of the mass by these two techniques is ≃10 per cent at most. There is no indication of any dependence of the mass ratio on the X-ray morphology of the clusters, indicating that the hydrostatic masses are not strongly systematically affected by the dynamical state of the clusters. Overall, our results favour a small value of the so-called hydrostatic bias due to non-thermal pressure sources.