Groundbreaking Discovery: Faint Radio Emission Unveiled in Low-Mass Galaxy Cluster

The southern relic in the cluster is thought to be formed by shock passage, while the northern relic has an elongated structure and the presence of several radio galaxies suggests that fossil electrons from the radio galaxy contributed to its formation.

7 May 2024

By Payoshi Bisht

A team of astronomers from the Indian Institute of Technology (IIT), Indore under the leadership of Dr. Swarna Chatterjee, have detected a faint radio emission over 2 million light years in the Abell 2108 low mass galaxy cluster near Pune, using the upgraded Giant metrewave radio telescope (uGMR). This makes the cluster a unique double radio relic system and provides important information on the formation and development of galaxy clusters. 

The article was published in the latest issue of the Monthly Notices of the Royal Astronomers of Journal (MNRAS) of Oxford University Press. 

The importance of low mass galaxy clusters, such as A2108, remains largely unexplored despite their importance in understanding the formation of early universe clusters and the interactions between magnetic fields and cosmic rays and the inner cluster medium. 

The discovery aims to offer important insights into galaxy clusters’ formation and evolution. GMRT, one of the ‘pathfinder’ telescopes, contributes to the development of advanced techniques for the Square Kilometer Array (SKA), a global mega science project.

This discovery is part of a larger survey effort known as ‘uGMRT low mass cluster survey’ that addresses the extremely difficult challenge of studying diffuse radio emission from low mass galaxy clusters.

Dr. Chatterjee, a PhD student, conducted the research in collaboration with Dr. Abhiralup Datta, another PhD student, both from IIT Indore, in partnership with Dr. Majidul Ruhaman (PhD Student) from the National Tsing Hua University of Science and Technology, Taiwan as well as Dr. Rutra Kale (PhD Researcher) from National Centre for Radio Astrophysics (NCRA), Pune and Dr. Surajit (PhD Practitioner) from Manipal Academy of Higher Education (MAHE), Manipal, who is the Principal Investigator (PI) of the GLOMACS project. 

The low-mass Abell 2108 cluster was originally thought to contain a radio relic located in the southern part of the cluster. However, a new observation by the team led by Dr. Chatterjee revealed another faint and patchy radio structure in the northern part of Abell 2108, identifying it as one of the few double radio relic systems. 

The newly identified structure is two times more massive than the southern relic and is among the ten faintest radio relics observed to date. The researchers also detected a faint shock at the location of the relic through X-ray observations using the XMM- Newton X-Ray telescope.