A powerful radio halo in the hottest known cluster of galaxies 1E 0657-56

We report the detection of a diffuse radio halo source in the hottest known cluster of galaxies 1E 0657-56 (RX J0658-5557). The radio halo has a morphology similar to the X-ray emission from the hot intracluster medium. The presence of a luminous radio halo in such a hot cluster is further evidence for a steep correlation between the radio halo power and the X-ray temperature. We favor models for the origin of radio halo sources involving a direct connection between the X-ray emitting thermal particles and the radio emitting relativistic particles.