Hydrostatic mass profiles of galaxy clusters in the eROSITA survey

¹ Max-Planck-Institut für extraterrestrische Physik, Gießenbachstraße 1, 85748 Garching, Germany
e-mail: dominik.ck@dg-email.de
² Technical University of Munich, Department of Physics, James-Franck-Straße 1, 85748 Garching, Germany
³ INAF – Osservatorio Astronomico di Trieste, via Tiepolo 11, 34143 Trieste, Italy
⁴ Universitäts-Sternwarte, Fakultät für Physik, Ludwig-Maximilians-Universität München, Scheinerstr.1, 81679 München, Germany
⁵ Max-Planck-Institut für Astrophysik, Karl-Schwarzschild-Straße 1, 85741 Garching, Germany

Received: 22 July 2022
Accepted: 11 November 2022

Abstract

Context. To assume hydrostatic equilibrium between the intracluster medium and the gravitational potential of galaxy clusters is an extensively used method to investigate their total masses.

Aims. We want to test hydrostatic masses obtained with an observational code in the context of the Spectrum-Roentgen-Gamma/eROSITA survey.

Methods. We used the hydrostatic modeling code MBProj2 to fit surface-brightness profiles to simulated clusters with idealized properties as well as to a sample of 93 clusters taken from the Magneticum Pathfinder simulations. We investigated the latter under the assumption of idealized observational conditions and also for realistic eROSITA data quality. The comparison of the fitted cumulative total mass profiles and the true mass profiles provided by the simulations allows us to gain knowledge both about the validity of hydrostatic equilibrium in each cluster and the reliability of our approach. Furthermore, we used the true profiles for gas density and pressure to compute hydrostatic mass profiles based on theory for every cluster.

Results. For an idealized cluster that was simulated to fulfill perfect hydrostatic equilibrium, we find that the cumulative total mass at the true r₅₀₀ and r₂₀₀ can be reproduced with deviations of less than 7%. For the clusters from the Magneticum Pathfinder simulations under idealized observational conditions, the median values of the fitted cumulative total masses at the true r₅₀₀ and r₂₀₀ are in agreement with our expectations, taking into account the hydrostatic mass bias. Nevertheless, we find a tendency towards steeper cumulative total mass profiles in the outskirts than expected. For realistic eROSITA data quality, this steepness problem intensifies for clusters with high redshifts and leads to excessive cumulative total masses at r₂₀₀. For the hydrostatic masses based on the true profiles known from the simulations, we find good agreement with our expectations concerning the hydrostatic mass.