Turbulent pressure support in galaxy clusters

Impact of the hydrodynamical solver

¹ Universitäts-Sternwarte, Fakultät für Physik, Ludwig-Maximilians-Universität München, Scheinerstr. 1, 81679 München, Germany
² Astronomy Unit, Department of Physics, University of Trieste, via Tiepolo 11, I-34131 Trieste, Italy
³ INAF – Osservatorio Astronomico di Trieste, via Tiepolo 11, I-34131 Trieste, Italy
⁴ ICSC – Italian Research Center on High Performance Computing, Big Data and Quantum Computing, via Magnanelli 2, 40033 Casalecchio di Reno, Italy
⁵ Center for Computational Astrophysics, Flatiron Institute, 162 Fifth Avenue, New York, NY 10010, USA
⁶ Departament d’Astronomia i Astrofísica, Universitat de València, C/Doctor Moliner 50, E-46100 Burjassot (València), Spain
⁷ Max-Planck-Institut für Astrophysik, Karl-Schwarzschild-Straße 1, 85741 Garching, Germany

^⋆ Corresponding author; fgroth@usm.lmu.de

Received: 5 August 2024
Accepted: 5 December 2024

Abstract

Context. The amount of turbulent pressure in galaxy clusters is still debated, especially in relation to the impact of the dynamical state and the hydro-method used for simulations.

Aims. We study the turbulent pressure fraction in the intracluster medium of massive galaxy clusters. We aim to understand the impact of the hydrodynamical scheme, analysis method, and dynamical state on the final properties of galaxy clusters from cosmological simulations.

Methods. We performed non-radiative simulations of a set of zoom-in regions of seven galaxy clusters with meshless finite mass (MFM) and smoothed particle hydrodynamics (SPH). We used three different analysis methods based on: (i) the deviation from hydrostatic equilibrium, (ii) the solenoidal velocity component obtained by a Helmholtz-Hodge decomposition, and (iii) the small-scale velocity obtained through a multi-scale filtering approach. We split the sample of simulated clusters into active and relaxed clusters.

Results. Our simulations predict an increased turbulent pressure fraction for active clusters compared to relaxed ones. This is especially visible for the velocity-based methods. For these, we also find increased turbulence for the MFM simulations compared to SPH, consistent with findings from more idealized simulations. The predicted nonthermal pressure fraction varies between a few percent for relaxed clusters and ≈13% for active ones within the cluster center and increases toward the outskirts. No clear trend with redshift is visible.

Conclusions. Our analysis quantitatively assesses the importance played by the hydrodynamical scheme and the analysis method to determine the nonthermal or turbulent pressure fraction. While our setup is relatively simple (non-radiative runs), our simulations show agreement with previous, more idealized simulations, and represent a step closer to an understanding of turbulence.