The XXL Survey XI: ATCA 2.1 GHz continuum observations

TL;DR

This paper presents high-resolution 2.1 GHz radio imaging of a 6.5 deg^2 region in the XXL South field, cataloging 1389 sources and analyzing their properties to support future large-scale surveys and galaxy evolution studies.

Contribution

It provides the first detailed radio continuum catalog for the XXL South field at 2.1 GHz, including spectral index measurements and source characterization, as a pilot for larger future surveys.

Findings

1389 radio sources identified with S/N >= 5

Average spectral index of -0.78 with scatter 0.28

Source counts agree with previous surveys like COSMOS-VLA

Abstract

We present 2.1 GHz imaging with the Australia Telescope Compact Array (ATCA) of a 6.5 deg^2 region within the XXM-Newton XXL South field using a band of 1.1-3.1 GHz. We achieve an angular resolution of 4.7" x 4.2" in the final radio continuum map with a median rms noise level of 50 uJy/beam. We identify 1389 radio sources in the field with peak S/N >=5 and present the catalogue of observed parameters. We find that 305 sources are resolved, of which 77 consist of multiple radio components. These number counts are in agreement with those found for the COSMOS-VLA 1.4 GHz survey. We derive spectral indices by a comparison with the Sydney University Molongolo Sky Survey (SUMSS) 843MHz data. We find an average spectral index of -0.78 and a scatter of 0.28, in line with expectations. This pilot survey was conducted in preparation for a larger ATCA program to observe the full 25 deg^2 southern XXL field. When complete, the survey will provide a unique resource of sensitive, wide-field radio continuum imaging with complementary X-ray data in the field. This will facilitate studies of the physical mechanisms of radio-loud and radio-quiet AGNs and galaxy clusters, and the role they play in galaxy evolution. The source catalogue is publicly available online via the XXL Master Catalogue browser and the Centre de Donn\'ees astronomiques de Strasbourg (CDS).