Discovery of large-scale radio emission enveloping the mini-halo in the most X-ray luminous galaxy cluster RX~J1347.5-1145

TL;DR

This study reveals a large-scale radio halo surrounding a mini-halo in galaxy cluster RX J1347.5-1145, combining multi-frequency radio and X-ray data to explore their origins and the mechanisms behind their formation.

Contribution

It provides the first detailed multi-wavelength analysis confirming the coexistence of a mini-halo and a large radio halo, and discusses their distinct formation mechanisms.

Findings

The radio emission extends up to 1 Mpc in size.

The mini-halo and halo have different spectral and brightness correlations.

The halo's properties support a turbulent origin, while the mini-halo may involve turbulent and hadronic processes.

Abstract

Diffuse radio sources, known as mini-halos and halos, are detected at the centres of galaxy clusters. These centralized diffuse sources are typically observed individually, with both appearing together only in rare cases. The origin of the diffuse radio sources in such systems remains unclear. We investigate the formation of large-scale radio emission in the most X-ray luminous, massive galaxy cluster RXJ~1347.5-1145 which is known to host a mini-halo at its centre and possibly additional more extended emission. We conduct deep multi-frequency observations of the galaxy cluster using the MeerKAT at 1.28 GHz and the uGMRT (upgraded Giant Metrewave Radio Telescope) at 1.26 GHz and 700 MHz. We characterize the brightness and spectral properties of the central diffuse sources and combine our radio observations with \textit{Chandra} X-ray data to explore the correlation between the cluster's non-thermal and thermal emissions. We confirm the presence of the diffuse emission and find that it extends up to 1~Mpc in size. Our multi-wavelength data reveal that the central diffuse emission consists of two distinct components: a mini-halo located in the cluster core and a larger radio halo extending around it. The correlation between radio and X-ray surface brightness in both sources indicates a strong connection between the non-thermal and thermal properties of the ICM. The differing slopes in the $I_R-I_X$ and $\alpha-I_X$ relations suggest that distinct mechanisms are responsible for the formation of the mini-halo and halo. The properties of the halo align with the turbulent model, while both turbulent and hadronic processes may contribute to the formation of the mini-halo.