Abell 746: A Highly Disturbed Cluster Undergoing Multiple Mergers

May 2024 • 2024ApJ...966...38R

Authors • Rajpurohit, K. • Lovisari, L. • Botteon, A. • Jones, C. • Forman, W. • O'Sullivan, E. • van Weeren, R. J. • HyeongHan, K. • Bonafede, A. • Jee, M. J. • Vazza, F. • Brunetti, G. • Cho, H. • Domínguez-Fernández, P. • Stroe, A. • Finner, K. • Brüggen, M. • Vrtilek, J. M. • David, L. P. • Schellenberger, G. • Wittman, D. • Lusetti, G. • Kraft, R. • De Gasperin, F.

Abstract • We present deep XMM-Newton, Karl G. 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 (≤4 keV), likely due to a complex merger. We find evidence of three surface brightness edges and one candidate edge, of which three are merger-driven shock fronts. Combining our new data with published LOw-Frequency ARray observations has unveiled the nature of diffuse sources in this system. The bright NW relic shows thin filaments and a 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 the shock-heated regions and a 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. A 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.

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Kyle Finner

Postdoctoral Research Associate