# Low-frequency radio study of MACS clusters at 610 and 235 MHz using the GMRT

## TL;DR

This study uses GMRT dual-frequency radio observations to investigate the diffuse radio emissions in four high-redshift galaxy clusters, revealing new relics, a mini-halo, and detailed spectral properties that shed light on cluster mergers and intra-cluster medium dynamics.

## Contribution

First low-frequency GMRT observations of MACS clusters revealing new relics, mini-halo, and spectral signatures, advancing understanding of cluster mergers at high redshift.

## Key findings

- Discovery of a faint, elongated radio source in MACSJ0152.5-2852.
- Confirmation of a relic-like source in MACSJ0025.4-1222.
- Detection of a mini-halo and bent jets in MACSJ1931-2635.

## Abstract

Studies have shown that mergers of massive galaxy clusters produce shocks and turbulence in the intra-cluster medium, the possible event that creates radio relics, as well as the radio halos. Here we present 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 MACSJ0025.4-1222 cluster. Proposed relics in both these clusters are found apparently inside the virial radius instead of their usual peripheral location, while no radio halos are detected. These high-redshift clusters ($z=0.584$ and $0.413$) are among the earliest merging systems detected with cluster radio emissions. In MACSJ1931-2635 cluster, we found a radio mini-halo and an interesting highly bent pair of radio jets. Further, we present here a maiden study of low frequency (GMRT $235\;\&\;610$~MHz) spectral and morphological signatures of a previously known radio cluster MACSJ0014.3-3022 (Abell~2744). This cluster hosts a relatively flat spectrum ($\alpha^{610}_{235}\sim -1.15$), giant ($\sim 1.6$~Mpc each) halo-relic structure and a close-by high-speed ($1769\pm^{148}_{359}$~km~s$^{-1}$) merger-shock ($\mathcal{M}=2.02\pm^{0.17}_{0.41}$) originated from a possible second merger in the cluster.