Mapping the Perseus galaxy cluster with XRISM

Gas kinematic features and their implications for turbulence

¹ Department of Theoretical Physics and Astrophysics, Masaryk University Brno 61137, Czechia
² Department of Astronomy and Astrophysics, The University of Chicago Chicago IL 60637, USA
³ Center for Astrophysics | Harvard-Smithsonian MA 02138, USA
⁴ Center for Space Sciences and Technology, University of Maryland, Baltimore County (UMBC) Baltimore MD 21250, USA
⁵ NASA/Goddard Space Flight Center Greenbelt MD 20771, USA
⁶ Center for Research and Exploration in Space Science and Technology, NASA/GSFC (CRESST II) Greenbelt MD 20771, USA
⁷ Max Planck Institute for Astrophysics Karl-Schwarzschild-Str. 1 D-85741 Garching, Germany
⁸ Space Research Institute (IKI) Profsoyuznaya 84/32 Moscow 117997, Russia
⁹ Lawrence Livermore National Laboratory Livermore CA 94550, USA
¹⁰ Department of Physics, Tokyo Metropolitan University Tokyo 192-0397, Japan
¹¹ Département de Physique, Université de Montréal, Succ. Centre-Ville, Montréal Québec H3C 3J7, Canada
¹² RIKEN Nishina Center Saitama 351-0198, Japan
¹³ Faculty of Physics, Tokyo University of Science Tokyo 162-8601, Japan
¹⁴ IRAP, CNRS, Université de Toulouse, CNES, UT3-UPS Toulouse, France
¹⁵ Kavli Institute for Astrophysics and Space Research, Massachusetts Institute of Technology Cambridge MA 02139, USA
¹⁶ Faculty of Engineering, University of Miyazaki Miyazaki 889-2192, Japan
¹⁷ College of Science and Engineering, Kanto Gakuin University Kanagawa 236-8501, Japan
¹⁸ Department of Astronomy, University of Maryland, College Park MD 20742, USA
¹⁹ Faculty of Mathematics and Physics, Kanazawa University, Kanazawa Ishikawa 920-1192, Japan
²⁰ Advanced Research Center for Space Science and Technology, Kanazawa University, Kanazawa Ishikawa 920-1192, Japan
²¹ Academia Sinica Institute of Astronomy and Astrophysics (ASIAA) Taipei 106319, Taiwan

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

Received: 11 October 2025
Accepted: 4 December 2025

Abstract

We present extended gas kinematic maps of the Perseus cluster based on a combination of five new XRISM/Resolve pointings observed in 2025 with four performance verification datasets from 2024, totaling a net exposure of 745 ks. To date, Perseus remains the only cluster that has been extensively mapped out to ≃0.7r₂₅₀₀ by XRISM/Resolve, while simultaneously offering sufficient spatial resolution to resolve gaseous substructures driven by mergers and active galactic nucleus (AGN) feedback. Our observations cover multiple radial directions and a broad range of dynamical scales, enabling us to characterize the kinematic properties of the intracluster medium up to a scale of ∼500 kpc. In the measurements, we detected high-velocity dispersions (≃300km s⁻¹) in the eastern region of the cluster that are spatially coincident with the extended X-ray surface brightness excess and correspond to a nonthermal pressure fraction of ≃7 − 13%. The velocity field outside the AGN-dominant region can be effectively described by a single, large-scale kinematic driver based on the velocity structure function, which statistically favors an energy injection scale of at least a few hundred kpc. The estimated turbulent dissipation energy is comparable to the gravitational potential energy released by a recent merger, implying a significant role of turbulent cascade in the merger energy conversion. In the bulk velocity field, we observed a dipole-like pattern along the east-west direction with an amplitude of ≃ ± 200 − 300 km s⁻¹, indicating rotational motions induced by the recent merger event. This feature constrains the viewing direction to ≃30° −50° relative to the normal of the merger plane. Our hydrodynamic simulations suggest that Perseus has experienced at least two energetic mergers since redshift z ∼ 1, the most recent of which is associated with the radio galaxy IC310, in agreement with recent SRG/eROSITA findings. This study showcases exciting scientific opportunities for future missions with high-resolution spectroscopic capabilities (e.g., HUBS, LEM, and NewAthena).