2019MNRAS.489..446P

Studies have shown that mergers of massive galaxy clusters produce shocks and turbulence in the intracluster medium, these events possibly creating radio relics, as well as radio haloes. Here we present Giant Metrewave Radio Telescope (GMRT) dual-band (235- and 610-MHz) radio observations of four such clusters from the MAssive Cluster Survey (MACS) catalogue. We report the discovery of a very faint, diffuse, elongated radio source with a projected size of about 0.5 Mpc in cluster MACSJ0152.5-2852. We also confirm the presence of a radio-relic-like source (about 0.4 Mpc, previously reported at 325 MHz) in cluster MACSJ0025.4-1222. Proposed relics in both these clusters are found apparently inside the virial radius, instead of at their usual peripheral location, while no radio haloes are detected. These high-redshift clusters (z = 0.584 and 0.413) are among the earliest merging systems detected from cluster radio emission. In cluster MACSJ1931.8-2635, we found a radio mini-halo and an interesting highly bent pair of radio jets. Also, we present here a maiden study of low-frequency (GMRT 235- and 610-MHz) spectral and morphological signatures of the previously known radio cluster MACSJ0014.3-3022 (Abell 2744). This cluster hosts a relatively flat spectrum (α⁶¹⁰₂₃₅∼-1.15), giant (∼1.6 Mpc each) halo-relic structure and a nearby high-speed (1769±¹⁴⁸₃₅₉ km s^–1) merger shock ( M=2.02±^0.17_0.41) originating from a possible second merger in the cluster.