Resolving the hydrostatic mass profiles of galaxy clusters at z ∼ 1 with XMM-Newton and Chandra

¹ IRFU, CEA, Université Paris-Saclay, 91191 Gif-Sur-Yvette, France
e-mail: iacopo.bartalucci@cea.fr
² Université Paris Diderot, AIM, Sorbonne Paris Cité, CEA, CNRS, 91191 Gif-sur-Yvette, France

Received: 13 December 2017
Accepted: 7 May 2018

Abstract

We present a detailed study of the integrated total hydrostatic mass profiles of the five most massive M₅₀₀^SZ < 5 × 10¹⁴ M_⊙ galaxy clusters selected at z ∼ 1 via the Sunyaev–Zel’dovich effect. These objects represent an ideal laboratory to test structure formation models where the primary driver is gravity. Optimally exploiting spatially-resolved spectroscopic information from XMM-Newton and Chandra observations, we used both parametric (forward, backward) and non-parametric methods to recover the mass profiles, finding that the results are extremely robust when density and temperature measurements are both available. Our X-ray masses at R₅₀₀ are higher than the weak lensing masses obtained from the Hubble Space Telescope (HST), with a mean ratio of 1.39_−0.35^+0.47. This offset goes in the opposite direction to that expected in a scenario where the hydrostatic method yields a biased, underestimated, mass. We investigated halo shape parameters such as sparsity and concentration, and compared to local X-ray selected clusters, finding hints for evolution in the central regions (or for selection effects). The total baryonic content is in agreement with the cosmic value at R₅₀₀. Comparison with numerical simulations shows that the mass distribution and concentration are in line with expectations. These results illustrate the power of X-ray observations to probe the statistical properties of the gas and total mass profiles in this high mass, high-redshift regime.