A&A 506, 1083-1094 (2009)
DOI: 10.1051/0004-6361/200912287

Radio observations of ZwCl 2341.1+0000: a double radio relic cluster

R. J. van Weeren¹, H. J. A. Röttgering¹, J. Bagchi², S. Raychaudhury³, H. T. Intema¹, F. Miniati⁴, T. A. Enßlin⁵, M. Markevitch⁶, and T. Erben<sup>7

1</sup>  Leiden Observatory, Leiden University, PO Box 9513, 2300 RA Leiden, The Netherlands
    e-mail: rvweeren@strw.leidenuniv.nl
²  Inter-University Centre for Astronomy and Astrophysics (IUCAA), Pune 411007, India
³  School of Physics and Astronomy, University of Birmingham, Edgbaston, Birmingham B15 2TT, UK
⁴  Physics Department, Wolfgang-Pauli-Strasse 27, ETH-Zürich, 8093 Zürich, Switzerland
⁵  Max-Planck-Institut für Astrophysik, Karl-Schwarzschild-Str.1, PO Box 1317, 85741 Garching, Germany
⁶  Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA
⁷  Argelander-Institut für Astronomie, Universität Bonn, Auf dem Hügel 71, 53121 Bonn, Germany

Received 6 April 2009 / Accepted 30 July 2009

Abstract
Context. Hierarchal models of large-scale structure (LSS) formation predict that galaxy clusters grow via gravitational infall and mergers of smaller subclusters and galaxy groups. Diffuse radio emission, in the form of radio halos and relics, is found in clusters undergoing a merger, indicating that shocks or turbulence associated with the merger are capable of accelerating electrons to highly relativistic energies. Double relics are a rare class of radio sources found in the periphery of clusters, with the two components located symmetrically on the opposite sides of the cluster center. These relics are important probes of the cluster periphery as (i) they provide an estimate of the magnetic field strength, and (ii) together with detailed modeling can be used to derive information about the merger geometry, mass, and timescale. Observations of these double relics can thus be used to test the framework of LSS formation. Here we report on radio observations of ZwCl 2341.1+0000 , a complex merging structure of galaxies located at z=0.27, using Giant Metrewave Radio Telescope (GMRT) observations.
Aims. The main aim of the observations is to study the nature of the diffuse radio emission in the galaxy cluster ZwCl 2341.1+0000 .
Methods. We carried out GMRT 610, 241, and 157 MHz continuum observations of ZwCl 2341.1+0000 . The radio observations are combined with X-ray and optical data of the cluster.
Results. The GMRT observations show a double peripheral radio relic in the cluster ZwCl 2341.1+0000 . The spectral index is for the northern relic and for the southern relic. We have derived values of 0.48-0.93 Gauss for the equipartition magnetic field strength. The relics are probably associated with outward traveling merger shock waves.


Key words: radio continuum: galaxies -- galaxies: active -- galaxies: clusters: individual: ZwCl 2341.1+0000 -- cosmology: large-scale structure of Universe

© ESO 2009

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