# Gas sloshing in Abell 2204: Constraining the properties of the magnetized intracluster medium

## TL;DR

This study analyzes X-ray observations of galaxy cluster Abell 2204 to understand the properties of its intracluster medium, revealing evidence of magnetic field amplification that suppresses Kelvin-Helmholtz instabilities at cold fronts.

## Contribution

It provides the first detailed measurement of magnetic field strengths in the cold fronts of Abell 2204, linking sloshing motions to magnetic field amplification.

## Key findings

- Cold front density and temperature ratios are typical of galaxy clusters.
- Magnetic fields are estimated to be greater than 24 and 32 μG at the cold fronts.
- Kelvin-Helmholtz instabilities are suppressed, likely by magnetic fields.

## Abstract

The rich galaxy cluster Abell 2204 exhibits edges in its X-ray surface brightness at $\sim 65$ and $35 {\rm~ kpc}$ west and east of its center, respectively. The presence of these edges, which were interpreted as sloshing cold fronts, implies that the intracluster medium was recently disturbed. We analyze the properties of the intracluster medium using multiple Chandra observations of Abell 2204. We find a density ratio $n_{\rm in}/n_{\rm out} = 2.05\pm0.05$ and a temperature ratio $T_{\rm out}/T_{\rm in} = 1.91\pm0.27$ (projected, or $1.87\pm0.56$ deprojected) across the western edge, and correspondingly $n_{\rm in}/n_{\rm out} = 1.96\pm0.05$ and $T_{\rm out}/T_{\rm in} =1.45\pm0.15$ (projected, or $1.25\pm0.26$ deprojected) across the eastern edge. These values are typical of cold fronts in galaxy clusters. This, together with the spiral pattern observed in the cluster core, supports the sloshing scenario for Abell 2204. No Kelvin-Helmholtz eddies are observed along the cold front surfaces, indicating that they are effectively suppressed by some physical mechanism. We argue that the suppression is likely facilitated by the magnetic fields amplified in the sloshing motion, and deduce from the measured gas properties that the magnetic field strength should be greater than $24\pm6$ $\mu$G and $32\pm8$ $\mu$G along the west and east cold fronts, respectively.