Radio halos in galaxy clusters: The interesting case of Abell 2142

T. Venturi1, M. Rossetti2, D. Vir Lal3, S. Giacintucci4, D. Eckert5, F. Gastaldello6,7, S. Molendi6, D. Farnsworth8 and L. Rudnick8
1INAF, Istituto di Radioastronomia, Via Gobetti 101, 40129 Bologna, Italy
2Universit`d degli studi di Milano, Dip. di Fisica, Via Celoria 16, 20133 Milano, Italy 3NCRA, TIFR, Pune University Campus, Pune, India
4Department of Astronomy, University of Maryland, College Park, MD20742-2421, USA
5Department of Astronomy, University of Geneva, ch. d’Ecologia 16, 1290 Versoix, Switzerland
6INAF, IASF-Milano, Via Bassini 15, 20133 Milano, Italy
7Department of Physics and Astronomy, UC at Irvine, 4129 Frederick Reines Hall, Irvine, CA 92697-4572, USA
8Minnesota Institute for Astrophysics, University of Minnesota, 116 Church Street S.E., Minneapolis, MN 55455, USA

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We present GMRT deep observations at 610 MHz and 325 MHz of the galaxy cluster Abell 2142, where a giant radio halo of extremely low surface brightness has been recently detected at 1.4 GHz with the Green Bank Radio Telescope (GBT). Comparison with a re-analysis of archival 1.4 GHz VLA data show that the spectrum of the radio halo is very steep between 325 MHz and 1.4 GHz. A2142 is not a major merger, at odds with the very unrelaxed dynamical state of the galaxy clusters hosting giant radio halos. A new cold front, located at about 1 Mpc from the cluster centre, has been recently found with XMM–Newton observations, suggesting that the cluster is characterised by gas sloshing motion at all scales, following an o –axis minor merger. We propose that either the sloshing itself or the turbulence induced by the minor merger may be at the origin of the giant radio halo.

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Keywords : galaxies: clusters: general – galaxies: clusters: individual: A2141 – radio continuum: general