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

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. A 2142 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 off-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.