Abell 746: A highly disturbed cluster undergoing multiple mergers

TL;DR

This study uses multi-wavelength observations to analyze the complex merger activity, shock fronts, and diffuse radio emissions in Abell 746, revealing its highly disturbed state and the interplay between thermal and nonthermal phenomena.

Contribution

The paper provides a detailed multi-wavelength analysis of Abell 746, uncovering multiple merger-driven shock fronts and complex diffuse radio emissions, advancing understanding of cluster merger dynamics.

Findings

Identification of four surface brightness edges, including three shock fronts.

Detection of a radio relic with high polarization and filamentary structure.

Observation of a large-scale radio halo and anticorrelation between radio and X-ray features.

Abstract

We present deep XMM-Newton, Karl Jansky Very Large Array, and upgraded Giant Metrewave Radio Telescope observations of Abell 746, a cluster that hosts a plethora of diffuse emission sources that provide evidence for the acceleration of relativistic particles. Our new XMM-Newton images reveal a complex morphology of the thermal gas with several substructures. We observe an asymmetric temperature distribution across the cluster: the southern regions exhibit higher temperatures, reaching ~9 keV, while the northern regions have lower temperatures (below 4 keV), likely due to a complex merger. We find evidence of four surface brightness edges, of which three are merger-driven shock fronts. Combining our new data with the published LOw-Frequency ARray observations has unveiled the nature of diffuse sources in this system. The bright northwest relic shows thin filaments and high degree of polarization with aligned magnetic field vectors. We detect a density jump, aligned with the fainter relic to the north. To the south, we detect high-temperature regions, consistent with shock-heated regions and density jump coincident with the northern tip of the southern radio structure. Its integrated spectrum shows a high-frequency steepening. Lastly, we find that the cluster hosts large-scale radio halo emission. The comparison of the thermal and nonthermal emission reveals an anticorrelation between the bright radio and X-ray features at the center. Our findings suggest that Abell 746 is a complex system that involves multiple mergers.