Unveiling Complexity in the Abell 85 Cluster: Radio Phoenixes, Minihalos, and Shock Compression

Majidul Rahaman^1*, Ramij Raja²

¹Institute of Astronomy, National Tsing Hua University, Hsinchu, Taiwan
²Centre for Radio Astronomy Techniques and Technologies, Department of Physics and Electronics, Rhodes University, Makhanda, South Africa

* Presenter:Majidul Rahaman, email:rmajidul@gmail.com

The Abell 85 cluster serves as a remarkable astrophysical laboratory, offering insights into various phenomena within galaxy clusters. Our recent studies have uncovered the complexity of this cluster's dynamics. High-resolution 325 MHz GMRT radio maps revealed its intricate and filamentary structure. Confirming its presence, a bow shock was detected using Chandra X-ray observations. A comparison of Mach numbers derived from X-ray and radio data indicated remarkable consistency. Our deep observations at 700 MHz (GMRT) and L-band (MeerKAT) unveiled the presence of a radio bridge that connects the central minihalo to a peripheral radio phoenix. The origin of the relativistic electrons contributing to the bridge remains an open question, with turbulence associated with gas dynamics and merging shocks as potential mechanisms.
Also, high-resolution observations exposed finer filamentary structures, allowing the creation of spectral index maps. Furthermore, the steep integrated spectral index with a break at 700 MHz and varying spectral indices in filaments suggested recent re-energization and increased energy injection in specific regions. These findings collectively paint a comprehensive picture of Abell 85's complexity, demonstrating the interplay of radio phoenixes, minihalos, and shock compression in a dynamic cosmic environment. They significantly contribute to our understanding of galaxy cluster processes and underline the importance of multifaceted observational approaches in unravelling the mysteries of our universe.

Keywords: Galaxy clusters, X-ray shocks, Extragalactic radio sources, Astrophysics - High Energy Astrophysical Phenomena, Abell 85 cluster