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arXiv · 2602.21580

Bulk and turbulent gas motions in the interacting galaxy cluster Abell 3395 South observed with XRISM

Naomi Ota·Angie Veronica·Jakob Dietl·Anri Yanagawa·Thomas H. Reiprich·Veronica Biffi·Klaus Dolag·Marcus Brüggen·Esra Bulbul·Florian Pacaud·Yoshiki Toba
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Abstract

We investigate the gas motions in the core region of the Abell~3395 South subcluster (A3395S) using high-resolution X-ray spectroscopy with XRISM/Resolve. By analyzing the Fe~XXV He$\alpha$ emission line, we directly measure the line-of-sight bulk and turbulent velocities of the intracluster medium. We find that the one-dimensional turbulent velocity is low, at the level of $124\pm21~{\rm km\,s^{-1}}$, while a significant line-of-sight bulk velocity of $263\pm23~{\rm km\,s^{-1}}$ is detected. The coexistence of low turbulence and finite bulk motion suggests that A3395S has not yet reached a dynamically relaxed state. These results are consistent with the non-detection of a radio halo in A3395S, implying that turbulent particle reacceleration is currently inefficient in the cluster core. This study demonstrates that high-resolution X-ray spectroscopy with XRISM provides a powerful means to directly constrain intracluster medium dynamics in merging galaxy clusters, and it provides a reference for future comparative studies of A3395N and A3391 within the same large-scale structure.

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Naomi Ota, Angie Veronica, Jakob Dietl, Anri Yanagawa, Thomas H. Reiprich, Veronica Biffi, Klaus Dolag, Marcus Brüggen, Esra Bulbul, Florian Pacaud, Yoshiki Toba. 2026-02-25. Bulk and turbulent gas motions in the interacting galaxy cluster Abell 3395 South observed with XRISM. https://arxiv.org/abs/2602.21580

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