Hydrostatic and Caustic Mass Profiles of Galaxy Clusters

Ben J. Maughan; Paul A. Giles; Kenneth J. Rines; Antonaldo Diaferio; Margaret J. Geller; Nina Van Der Pyl; Massimiliano Bonamente

doi:10.1093/mnras/stw1610

paper

Hydrostatic and Caustic Mass Profiles of Galaxy Clusters

arXiv:1511.07872 · doi:10.1093/mnras/stw1610

Abstract

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 $\approx 20%$ on average across the radial range covered by both techniques $(\sim [0.2 - 1.25] R_{500})$ . The mass profiles were measured independently and do not assume a common functional form. Previous studies suggest that, at $R_{500}$ , the hydrostatic and caustic masses are biased low and high respectively. We find that the ratio of hydrostatic to caustic mass at $R_{500}$ is $1.2 0_{- 0.11}^{+ 0.13}$ ; thus it is larger than 0.9 at $\approx 3 σ$ and the combination of under- and over-estimation of the mass by these two techniques is $\approx 10%$ 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.

10 pages (including appendix), 6 figures. MNRAS in press

Hydrostatic and Caustic Mass Profiles of Galaxy Clusters

Abstract

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