Kinematics of the Weak Cool-Core Cluster A3571 Observed with XRISM: Low Cooling Rate Balanced by Low Heating Rate?

Most XRISM galaxy cluster observations to date have focused on AGN feedback or actively merging systems. The weak cool-core cluster A3571 was observed in four XRISM Cycle 1 pointings, enabling the study of gas kinematics in a relaxed, AGN-feedback-free system. We present measurements of the velocity dispersion and bulk velocity in the core regions of A3571, out to 120 kpc. The velocity dispersion is relatively uniform across all regions ( ∼ 100 − 120 k m s − 1 ), except in the northern gas sloshing elongation, where a 68 % upper limit of 68 k m s − 1 is obtained. The core Mach number and non-thermal pressure fraction of A3571 are lower than in the extremely relaxed cluster A2029 and below predictions from cosmological simulation suites. Despite relatively low velocity dispersion values, the derived turbulent heating rate (under the assumption of isotropic Kolmogorov turbulence) is sufficient to offset cooling losses within the considerable uncertainties in all studied regions. This suggests that sloshing motions may contribute significantly to the heating budget. Comparing XRISM observations of merging and relaxed clusters, we find that mergers exhibit an average Mach number of 0.29 ± 0.07 , nearly twice that of the relaxed sample, which is consistent with predictions from non-radiative cosmological simulations. A3571 is a promising target for resonant scattering studies; however, simulations indicate that deeper observations are required to obtain reliable turbulent velocities via the z / w line ratio.