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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.

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Monthly Notices of the Royal Astronomical Society



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This article has been accepted for publication in Monthly Notices of the Royal Astronomical Society ©: 2016 Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.