Kinetic structure of the intracluster medium across nearby clusters observed with XRISM
Naomi Ota, Erwin T. Lau, Satoshi Yamada, Yuki Omiya, Hiroya Yamaguchi
astro-ph.CO, astro-ph.GA, astro-ph.HE
Submitted: 2026-08-20
Updated: 2026-08-21
Comments: 6 pages, 2 figures, submitted to PASJ
License: http://creativecommons.org/licenses/by/4.0/
The gist: XRISM/Resolve is building a sample of galaxy clusters with directly measured ICM gas motions, revealing diverse projected dynamical states.
Terminology
Abstract
XRISM/Resolve is building a sample of galaxy clusters with directly measured ICM gas motions, revealing diverse projected dynamical states. We compile 45 XRISM/Resolve measurements in 19 nearby galaxy clusters and place them on a common, emission-weighted effective line-of-sight scale, eff. We compare the line-of-sight velocity dispersion sigma v, bulk velocity amplitude v bulk, their ratio R v v bulk/sigma v, and non-thermal pressure proxies. Disturbed non-cool-core systems are not simply higher-dispersion counterparts of relaxed cool-core regions. Instead, differences among cool-core centers, cool-core outer regions, and non-cool-core systems are driven mainly by coherent line-of-sight motion relative to unresolved line broadening: R v tends to remain below unity in cool-core regions but often exceeds unity in non-cool-core systems, with the mean R v rising from 0.45 in cool-core centers to 1.6 in non-cool-core systems. These diagnostics help separate local central line broadening, likely associated with AGN feedback in some cool cores, from larger-scale coherent motions associated with sloshing, mergers, and halo assembly. Comparison with forward-modeled TNG-Cluster predictions suggests that many cool-core measurements occupy the lower part of the predicted non-thermal pressure range, consistent with small hydrostatic-mass corrections in relaxed systems and larger corrections in disturbed ones. XRISM is thus beginning to resolve the projected kinetic structure of the ICM across cluster environments, rather than tracing a single sequence of increasing turbulence.
Sources
- The major cluster merger in Abell 2034 as seen by XRISM: Strong turbulence and spectral anomalies?
- Kinematics of the Weak Cool-Core Cluster A3571 Observed with XRISM: Low Cooling Rate Balanced by Low Heating Rate?
- Bulk and turbulent gas motions in the interacting galaxy cluster Abell 3395 South observed with XRISM
- XRISM Observations of Abell 1795: Evidence for Low Turbulence and Resonant Scattering
- The Quiescent Sloshing Core of Abell 496 with XRISM
- A Minimalist Merger Interpretation of XRISM's Gas Velocity Measurements in the Coma Cluster
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