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

¹ Hamburger Sternwarte, Universität Hamburg, Gojenbergsweg 112, 21029 Hamburg, Germany
² Academia Sinica Institute of Astronomy and Astrophysics No. 1, Section 4, Roosevelt Road, Taipei 10617, Taiwan
³ Thüringer Landessternwarte, Sternwarte 5, 07778 Tautenburg, Germany
⁴ Dipartimento di Fisica e Astronomia, Universitá di Bologna, via Gobetti 93/2, 40122 Bologna, Italy
⁵ INAF – Istituto di Radioastronomia di Bologna, Via Gobetti 101, I-40129 Bologna, Italy
⁶ Max Planck Institute for Extraterrestrial Physics, Giessenbachstrasse 1, 85748 Garching, Germany
⁷ Institute for Frontiers in Astronomy and Astrophysics, Beijing Normal University, Beijing 102206, China
⁸ Leiden Observatory, Leiden University, PO Box 9513, NL-2300 RA Leiden, The Netherlands

^⋆ Corresponding author; duyhoang.astro@gmail.com

Received: 29 August 2024
Accepted: 5 February 2025

Abstract

Context. Diffuse radio sources, known as mini-halos and halos, are detected at the centres of galaxy clusters. These centralised 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.

Aims. 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 and more extended emission.

Methods. We conducted deep multi-frequency observations of the galaxy cluster using MeerKAT at 1.28 GHz and the uGMRT at 1.26 GHz and 700 MHz. We characterised the brightness and spectral properties of the central diffuse sources and combined our radio observations with Chandra X-ray data to explore the correlation between the cluster’s non-thermal and thermal emissions.

Results. 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 the two sources indicates a strong connection between the non-thermal and thermal properties of the intracluster medium (ICM). The differing slopes in the I_R − I_X and α − I_X relations suggest that distinct mechanisms are responsible for the formation of the mini-halo and the 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.