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arXiv · 2601.05803

A Minimalist Merger Interpretation of XRISM's Gas Velocity Measurements in the Coma Cluster

Congyao Zhang·Eugene Churazov·Ildar Khabibullin·Natalya Lyskova·Norbert Werner·Irina Zhuravleva
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Abstract

The recent microcalorimetric X-ray observations of the Coma cluster by XRISM have sparked active discussion regarding the physical origin of its gas velocity features. Here, we demonstrate that an off-axis minor merger in its early phase $-$ when the infalling subhalo is near its primary apocenter and the stripped tail is not yet mixed with the main cluster atmosphere $-$ can drive intracluster gas motions generally consistent with the XRISM results. These include a pronounced velocity gradient and an approximately uniform velocity dispersion of $\simeq100-200\,\rm{km\,s^{-1}}$ in the cluster core. Our merger scenario was originally suggested in Lyskova et al. (2019) to reproduce the major X-ray morphological features of Coma. In addition, we introduce a simple and robust diagnostic of intracluster gas motions based on the ratio of the line-of-sight velocity to the velocity dispersion.

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Congyao Zhang, Eugene Churazov, Ildar Khabibullin, Natalya Lyskova, Norbert Werner, Irina Zhuravleva. 2026-01-09. A Minimalist Merger Interpretation of XRISM's Gas Velocity Measurements in the Coma Cluster. https://arxiv.org/abs/2601.05803

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