Abell 1033: birth of a radio phoenix

TL;DR

This paper reports the discovery of a newly formed radio phoenix in galaxy cluster Abell 1033, linked to a recent merger, supported by multi-wavelength observations revealing shock-induced reactivation of aged radio lobes.

Contribution

It presents the first observational evidence of a radio phoenix in formation, combining radio and X-ray data to connect merger shocks with reactivated radio emission.

Findings

Discovery of a radio phoenix near Abell 1033's merger site

Evidence of shocks and density discontinuity associated with the source

Support for the reactivation mechanism of aged radio lobes by merger shocks

Abstract

Extended steep-spectrum radio emission in a galaxy cluster is usually associated with a recent merger. However, given the complex scenario of galaxy cluster mergers, many of the discovered sources hardly fit into the strict boundaries of a precise taxonomy. This is especially true for radio phoenixes that do not have very well defined observational criteria. Radio phoenixes are aged radio galaxy lobes whose emission is reactivated by compression or other mechanisms. Here, we present the detection of a radio phoenix close to the moment of its formation. The source is located in Abell 1033, a peculiar galaxy cluster which underwent a recent merger. To support our claim, we present unpublished Westerbork Synthesis Radio Telescope and Chandra observations together with archival data from the Very Large Array and the Sloan Digital Sky Survey. We discover the presence of two sub-clusters displaced along the N-S direction. The two sub-clusters probably underwent a recent merger which is the cause of a moderately perturbed X-ray brightness distribution. A steep-spectrum extended radio source very close to an AGN is proposed to be a newly born radio phoenix: the AGN lobes have been displaced/compressed by shocks formed during the merger event. This scenario explains the source location, morphology, spectral index, and brightness. Finally, we show evidence of a density discontinuity close to the radio phoenix and discuss the consequences of its presence.