# A radio halo surrounding the Brightest Cluster Galaxy in RXCJ0232.2-4420: a mini-halo in transition ?

## TL;DR

This paper reports the discovery of a large diffuse radio source in galaxy cluster RXCJ0232.2-4420, which appears to be in transition from a mini-halo to a radio halo, providing insights into cluster magnetic fields and cosmic rays.

## Contribution

The study presents the first detection of a diffuse radio source with properties intermediate between mini-halos and radio halos in a galaxy cluster.

## Key findings

- Diffuse radio source surrounds the BCG like a mini-halo.
- The source's size is larger than typical mini-halos, similar to radio halos.
- The cluster's dynamical state is complex, indicating a transition phase.

## Abstract

Diffuse radio sources associated with the intra-cluster medium are direct probes of the cosmic ray electrons and magnetic fields. We report the discovery of a diffuse radio source in the galaxy cluster RXCJ0232.2-4420 (SPT-CL J0232-4421, $z=0.2836$) using 606 MHz observations with the Giant Metrewave Radio Telescope. The diffuse radio source surrounds the Brightest Cluster Galaxy in the cluster like typical radio mini-halos. However the total extent of it is $550\times800$ kpc$^{2}$, which is larger than mini-halos and similar to that of radio halos. The BCG itself is also a radio source with a marginally resolved core at $7''$ (30 kpc) resolution. We measure the 606 MHz flux density of the RH to be $52\pm5$ mJy. Assuming a spectral index of 1.3, the 1.4 GHz radio power is $4.5 \times 10^{24}$ W Hz$^{-1}$. The dynamical state of the cluster has been inferred to be "relaxed" and also as "complex" depending on the classification methods based on the morphology of the X-ray surface brightness. This system thus seems to be in the transition phase from a mini-halo to a radio halo.