Discovery of diffuse radio emission in the galaxy cluster A1689

¹ Dipartimento di Fisica, Università degli Studi di Cagliari, Cittadella Universitaria, 09042 Monserrato (CA), Italy
e-mail: vvacca@oa-cagliari.inaf.it
² INAF – Osservatorio Astronomico di Cagliari, Strada 54, Loc. Poggio dei Pini, 09012 Capoterra (Ca), Italy
³ Dipartimento di Astronomia, Università degli Studi di Bologna, via Ranzani 1, 40127 Bologna, Italy
⁴ INAF – Istituto di Radioastronomia, via P. Gobetti 101, 40129 Bologna, Italy
⁵ Kapteyn Astronomical Institute, University of Groningen, Landleven 12, Groningen, The Netherlands
⁶ Department of Physics and Astronomy, University of New Mexico, MSC 07 4220, Albuquerque, New Mexico, USA
⁷ Adjunct Astronomer at the National Radio Astronomy Observatory, Socorro, NM 87801, USA

Received: 30 June 2011
Accepted: 13 September 2011

Abstract

Aims. The aim of this work is to investigate the possible presence of extended diffuse synchrotron radio emission associated with the intracluster medium of the complex galaxy cluster A1689.

Methods. The radio continuum emission of A1689 has been investigated by analyzing archival observations at 1.2 and 1.4 GHz obtained with the Very Large Array in different configurations.

Results. We report the detection of an extended, diffuse, low-surface brightness radio emission located in the central region of A1689. The surface brightness profile of the diffuse emission at 1.2 GHz indicates a central radio brightness of  ≃ 1.7 μJy/arcsec² and the 3σ radio isophothes reveal the largest linear size to be 730 kpc. Given its central location, the low-level surface brightness, and the comparatively large extension, we classify the diffuse cluster-wide emission in A1689 as a small radio halo.