Tracing the merger history of MACS clusters using the GMRT

TL;DR

This study uses GMRT radio observations at two frequencies to investigate the merger history of MACS galaxy clusters, revealing complex radio relics and halos that trace their dynamical states and merging processes.

Contribution

It presents new radio observations of four MACS clusters, identifying rare and early-stage merger signatures through peripheral relics and central halos.

Findings

Detection of a rare peripheral radio relic and a flat-spectrum central halo in MACSJ0014.3-3022.

Identification of a faint peripheral relic in an early-stage merging cluster MACSJ0152.5-2852.

Simultaneous dual-frequency observations reveal detailed radio structures related to cluster mergers.

Abstract

Galaxy-cluster merger shocks efficiently accelerate the ambient electrons through diffusive shock acceleration and amplify magnetic field by compressing the Inter Cluster Medium. As a result, such objects produce a significant amount of synchrotron radio emission. Radio halo and Mpc scale peripheral radio relics thus help us to trace back the cluster formation history. To study the dynamical state of the galaxy clusters and their relation to the merging scenario, as a pilot project, we thus observed four suitable candidates from the MACS (Massive Cluster Survey) cluster sample. Observations were carried out simultaneously at 610 and 235 MHz with the GMRT. We observed a rare phenomena in the cluster MACSJ0014.3-3022, which hosts both a peripheral spectacular radio relic and an unusually flat spectrum central giant radio halo of more than 1.5 Mpc dimension. We also report that another cluster MACSJ0152.5-2852 is possibly showing the sign of one of the earliest and young merging system where, we saw a faint 0.5 Mpc radio relic at the cluster periphery.