The major cluster merger in Abell 2034 as seen by XRISM: Strong turbulence and spectral anomalies?

Annie Heinrich; Irina Zhuravleva; Eugene Churazov; Congyao Zhang; Daniele Rogantini; Hannah McCall; Reinout J. van Weeren; William R. Forman

doi:10.33232/001c.168514

arXiv · 2604.27161

The major cluster merger in Abell 2034 as seen by XRISM: Strong turbulence and spectral anomalies?

Annie Heinrich·Irina Zhuravleva·Eugene Churazov·Congyao Zhang·Daniele Rogantini·Hannah McCall·Reinout J. van Weeren·William R. Forman

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Abstract

XRISM observations to date have shown that gas kinetic pressures in the intracluster medium (ICM) tend towards the low end of predictions from cosmological simulations. Here, we present a XRISM observation of the merging cluster Abell 2034, which exhibits the broadest emission lines yet observed in a galaxy cluster. We measure a velocity dispersion of ~470 km/s, corresponding to a kinetic pressure fraction of ~15%. This places A2034 at or above the high end of the theoretical predictions for similar-mass clusters. This large velocity dispersion may reflect Mach ~0.5 turbulence in the ICM and/or result from a core disruption driven by the ongoing head-on merger. We also detect a ~380 km/s gas bulk velocity gradient along the merger axis with an opposite sign to the galaxy velocity gradient, indicating a decoupling of the cluster galaxies (and dark matter) from the ICM. Finally, we report tentative evidence of several spectral anomalies, including a suppressed Fe He$α$-z line, an enhanced Fe Ly$α$-2 line, and a potential absorption feature at ~8.7 keV. The first two features may be explained by the combination of a multi-component ICM and a non-equilibrium ionization state in the wake of a merger shock. Deeper XRISM observations of this cluster are required to confirm these features. This work highlights the importance of kinematic measurements across a large sample of merging clusters as well as the need for deep XRISM observations to unveil more exotic physics in the ICM.

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Annie Heinrich, Irina Zhuravleva, Eugene Churazov, Congyao Zhang, Daniele Rogantini, Hannah McCall, Reinout J. van Weeren, William R. Forman. 2026-08-20. The major cluster merger in Abell 2034 as seen by XRISM: Strong turbulence and spectral anomalies?. https://doi.org/10.33232/001c.168514

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