The XXL Survey: XXXIX. Polarised radio sources in the XXL-South field

TL;DR

This study characterizes the polarised radio source population in the XXL-South field at 2.1 GHz, analyzing source properties, their relation to X-ray clusters, and assessing the instrument's polarisation leakage effects.

Contribution

It provides the first detailed analysis of polarised radio sources in the XXL-South field at 2.1 GHz, including source counts, spectral indices, and instrumental leakage assessment.

Findings

39 polarised sources detected above 0.2 mJy

Number density of sources aligns with recent surveys, with an excess near 1 mJy

ATCA leakage is below 1.4% for mosaics with beam separation less than 2/3 of primary beam FWHM

Abstract

Aims: We investigate the properties of the polarised radio population in the central 6.5 deg$^{2}$ of the XXL-South field observed at 2.1 GHz using the Australia Telescope Compact Array (ATCA) in 81 pointings with a synthesised beam of FWHM 5.2''. We also investigate the ATCA's susceptibility to polarisation leakage. Methods: We performed a survey of a 5.6 deg$^{2}$ subregion and calculated the number density of polarised sources. We derived the total and polarised spectral indices, in addition to comparing our source positions with those of X-ray-detected clusters. We measured the polarisation of sources in multiple pointings to examine leakage in the ATCA. Results: We find 39 polarised sources, involving 50 polarised source components, above a polarised flux density limit of 0.2 mJy at 1.332 GHz. The number density of polarised source components is comparable with recent surveys, although there is an indication of an excess at $\sim1$ mJy. We find that those sources coincident with X-ray clusters are consistent in their properties with regard to the general population. In terms of the ATCA leakage response, we find that ATCA mosaics with beam separation of $\lesssim 2/3$ of the primary beam FWHM have off-axis linear polarisation leakage $\lesssim 1.4$ % at 1.332 GHz.