Letters to the Editor

A radio minihalo in the extreme cool-core galaxy cluster RXC J1504.1–0248

¹ INAF – Istituto di Radioastronomia, via Gobetti 101, 40129 Bologna, Italy
e-mail: sgiaci_s@ira.inaf.it
² Harvard-Smithsonian Centre for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA
³ Dip. Astronomia, University of Bologna, via Ranzani 1, 40127 Bologna, Italy

Received: 6 October 2010
Accepted: 12 November 2010

Abstract

Aims. We report the discovery of a radio minihalo in RXC J1504.1-0248, a massive galaxy cluster that has an extremely luminous cool core. To date, only 9 radio minihalos are known, thus the discovery of a new one in one of the most luminous cool-core clusters provides important information on this peculiar class of sources and sheds light on their origin.

Methods. The diffuse radio source was detected using GMRT at 327 MHz and confirmed by pointed VLA data at 1.46 GHz. The minihalo has a radius of ~140 kpc. A Chandra gas temperature map shows that the minihalo emission fills the cluster cool core and has some morphological similarities to it, as has been previously observed for other minihalos.

Results. The Chandra data reveal two subtle cold fronts in the cool core, likely created by sloshing of the core gas, as observed in most cool-core clusters. Following previous work, we speculate that the origin of the minihalo is related to sloshing. Sloshing may result in particle acceleration by generating turbulence and/or amplifying the magnetic field in the cool core, leading to the formation of a minihalo.