Complex diffuse radio emission in the merging PLANCK ESZ cluster Abell 3411

TL;DR

This study presents combined radio and X-ray observations of the merging galaxy cluster Abell 3411, revealing a radio halo and a complex, fragmented radio relic associated with merger shocks and possible re-acceleration of fossil electrons.

Contribution

First detailed radio and X-ray analysis of Abell 3411 showing complex diffuse radio emission linked to merger activity and shock interactions.

Findings

Discovery of a 0.9 Mpc radio halo in Abell 3411.

Identification of a 1.9 Mpc fragmented radio relic with complex morphology.

Spectral index of the combined radio emission is -1.0 ± 0.1.

Abstract

We present VLA radio and Chandra X-ray observations of the merging galaxy cluster Abell 3411. For the cluster, we find an overall temperature of 6.4 keV and an X-ray luminosity of 2.8 x 10^{44} erg s^{-1} between 0.5 and 2.0 keV. The Chandra observation reveals the cluster to be undergoing a merger event. The VLA observations show the presence of large-scale diffuse emission in the central region of the cluster, which we classify as a 0.9 Mpc size radio halo. In addition, a complex region of diffuse, polarized emission is found in the southeastern outskirts of the cluster, along the projected merger axis of the system. We classify this region of diffuse emission as a radio relic. The total extent of this radio relic is 1.9 Mpc. For the combined emission in the cluster region, we find a radio spectral index of -1.0 \pm 0.1 between 74 MHz and 1.4 GHz. The morphology of the radio relic is peculiar, as the relic is broken up into five fragments. This suggests that the shock responsible for the relic has been broken up due to interaction with a large-scale galaxy filament connected to the cluster or other substructures in the ICM. Alternatively, the complex morphology reflects the presence of electrons in fossil radio bubbles that are re-accelerated by a shock.