Astronomers from India and Taiwan conducted radio observations of the Abell 2108 galaxy cluster using the uGMRT radio telescope. They discovered a second radio artifact, much larger and with a different morphology than those previously seen in the cluster. The discovery was reported in an article published on the preprint server arXiv on December 7th. Radio relics are scattered elongated radio sources of synchrotronic origin. They occur in the form of single or double symmetrical arcs at the periphery of galaxy clusters. With a redshift of 0.09, Abell 2108 (A2108 for short) is a galaxy cluster with an estimated mass of about 301 trillion solar masses. Observations to date have shown that there is a radio relic approximately 980,000 x 390,000 light years in the southwest of this cluster. A team of astronomers led by Swarna Chatterjee from the Indian Institute of Technology Indore has reported the discovery of another radio relic in Abel 2108, making the cluster one of the few low-mass galaxy clusters with dual radio relics.
Chatterjee’s team discovered a distinct diffuse luminescent signature on Abel 2108’s northeastern fringes. The brightest region of this feature was measured to be about 1.4 million light-years away from the cluster’s X-ray center. The location and form of the radiation indicate that it is a radio relic. The discovered radio artifacts have a non-uniform structure. It covers twice the area of 1 million years and has an integrated magnetic flux density of 24.8 mJy. Observations show that both radio relics of Abel 2108 have significantly lower radiated power compared to other dual relic clusters, estimated at 1.4 GHz. Moreover, the results show that the surface brightness ratios of the two relics are different. This suggests that they may have different origins. Astronomers also detected an increase in surface brightness and a preliminary increase in temperature at the center of the radio relic in the northeast, suggesting there was a weak supersonic impact. This may explain the low radio brightness of the discovered artifacts.