Gas motion in the intracluster medium of the Virgo cluster replica

¹ Université Paris-Saclay, CNRS, Institut d’Astrophysique Spatiale, 91405 Orsay, France
² INAF, Osservatorio di Astrofisica e Scienza dello Spazio, Via Piero Gobetti 93/3, 40129 Bologna, Italy
³ INFN, Sezione di Bologna, Viale Berti Pichat 6/2, 40127 Bologna, Italy
⁴ Université de Lille, CNRS, Centrale Lille, UMR 9189 CRIStAL, F-59000 Lille, France

^★ Corresponding author: This email address is being protected from spambots. You need JavaScript enabled to view it.

Received: 17 June 2025
Accepted: 19 January 2026

Abstract

Within the deep gravitational potential of galaxy clusters lies the intracluster medium (ICM). At the first order, it is considered to be at hydrostatic equilibrium within the potential well. However, evidence is growing on the observational side and in numerical simulations that the ICM dynamics is non-negligible from an energetic point of view, is mostly turbulent in origin, and provides non-thermal pressure support to the equilibrium. In this work, we intend to characterise the properties of the velocity field in the ICM of a simulated replica of the Virgo cluster. We first studied the 3D and projected properties of the ICM velocity field by computing its probability density functions (PDFs) and its statistical moments. We then estimated the non-thermal pressure fraction from an effective turbulent Mach number, including the velocity dispersion. We finally computed the velocity structure function (VSF) from projected maps of the sightline velocity. In this paper, we first show that the components of the 3D velocity field and the projected quantities along equivalent sightlines are anisotropic and affected by the accretion of gas from filaments. Then, we compare the mean statistical moments of the 3D velocity field to the mean properties of 100 random projections. We show, in particular, an almost linear relation between the standard deviation estimated from direct simulation outputs and sightline velocity dispersion projections, which are comparable to the line broadening of X-ray atomic lines. However, this linear relation does not hold between the direct simulation outputs and the standard deviation of the sightline velocity projections, which are comparable to the line shift of X-ray atomic lines. We find a non-thermal pressure fraction of around 6% within R₅₀₀ and 9% within R_vir from sightline velocity dispersion, which is in good agreement with direct simulation outputs. Finally, we show that the VSF might probe the turbulent injection scale of active galactic nucleus (AGN) feedback.