Radio multifrequency observations of Abell~781 with the WSRT

TL;DR

This study uses high-sensitivity radio observations to investigate the complex merger activity in Abell 781, revealing extended emission and providing insights into the nature of peripheral radio features.

Contribution

First detailed polarimetric analysis of Abell 781 at multiple frequencies, identifying the nature of peripheral emission during a cluster merger.

Findings

Detected extended low-level radio emission at 21 cm.

Peripheral emission likely not a radio relic.

High-sensitivity polarimetric data obtained.

Abstract

The `Main' galaxy cluster in the Abell 781 system is undergoing a significant merger and accretion process with peripheral emission to the north and southeastern flanks of the merging structure. Here we present a full polarimetric study of this field, using radio interferometric data taken at 21 and 92 cm with the Westerbork Synthesis Radio Telescope, to a sensitivity better than any 21 cm (L-band) observation to date. We detect evidence of extended low-level emission of 1.9 mJy associated with the Main cluster at 21 cm, although this detection necessitates further follow-up by modern instruments due to the limited resolution of the Westerbork Synthesis Radio Telescope. Our polarimetric study indicates that, most likely, the peripheral emission associated with this cluster is not a radio relic.