The presence of non-thermal electrons and large scale magnetic fields in the intra-cluster medium (ICM) is known through the detection of mega-parsec (Mpc) scale diffuse radio synchrotron emission. Although a significant amount of progress in finding
new diffuse radio sources has happened in the last decade, most of the investigation has been constrained towards massive low-redshift clusters. In this work, we explore clusters with redshift $z>0.3$ in search of diffuse radio emission, at 325 MHz with the Giant Metrewave Radio Telescope (GMRT). This campaign has resulted in the discovery of 2 new radio halos (SPT-CL J0013-4906 and SPT-CL J0304-4401) along with 2 other detections (SPT-CL J2031-4037 and SPT-CL J2248-4431), previously reported (at 325 MHz) in the literature. In addition, we detect a halo candidate in 1 cluster in our sample, and upper limits for halos are placed in 8 clusters where no diffuse emission is detected. In the $P_{1.4} - L_mathrm{X}$ plane, the detected halos follow the observed correlation, whereas the upper limits lie above the correlation line, indicating the possibility of future detection with sensitive observations.
The advent of sensitive low frequency radio observations has revealed a number of diffuse radio objects with peculiar properties that are challenging our understanding about the physics of the intracluster medium. Here, we report the discovery of a s
teep spectrum radio halo surrounding the central Brightest Cluster Galaxy (BCG) in the galaxy cluster SPT-CL J2031-4037. This cluster is morphologically disturbed yet has a weak cool core, an example of cool core/non-cool core transition system, which harbours a radio halo of $sim 0.7$ Mpc in size. The halo emission detected at 1.7 GHz is less extended compared to that in the 325 MHz observation, and the spectral index of the part of the halo visible at 325 MHz to 1.7 GHz frequencies was found to be $-1.35 pm 0.07$. Also, $P_{1.4 mathrm{GHz}}$ was found to be $0.77 times 10^{24}$ W Hz$^{-1}$ which falls in the region where radio mini-halos, halo upper limits and ultra-steep spectrum (USS) halos are found in the $P_{1.4 mathrm{GHz}} - L_mathrm{X}$ plane. Additionally, simulations presented in the paper provide support to the scenario of the steep spectrum. The diffuse radio emission found in this cluster may be a steep spectrum intermediate or hybrid radio halo which is transitioning into a mini-halo.
Cool core galaxy clusters are considered to be dynamically relaxed clusters with regular morphology and highly X-ray luminous central region. However, cool core clusters can also be sites for merging events that exhibit cold fronts in X-ray and mini-
halos in radio. We present recent radio/X-ray observations of the Phoenix Cluster or SPT-CL J2344-4243 at the redshift of $z=0.596$. Using archival {it Chandra} X-ray observations, we detect spiraling cool gas around the cluster core as well as discover two cold fronts near the core. It is perhaps the most distant galaxy cluster to date known to host cold fronts. Also, we present JVLAfootnote{Jansky Very Large Array url{https://science.nrao.edu/facilities/vla}} 1.52 GHz observations of the minihalo, previously discovered at 610 MHz with GMRTfootnote{Giant Metrewave Radio Telescope url{http://www.gmrt.ncra.tifr.res.in}} observations in the center of the Phoenix galaxy cluster. The minihalo flux density at 1.52 GHz is $9.65 pm 0.97$ mJy with the spectral index between 610 MHz and 1.52 GHz being $-0.98 pm 0.16$footnote{$S_{ u} = u^{alpha}$ where $S_{ u}$}. A possible origin of these radio sources is turbulence induced by sloshing of the gas in the cluster core.
