The XXL Survey: XI. ATCA 2.1 GHz continuum observations

We present 2.1 GHz imaging with the Australia Telescope Compact Array (ATCA) of a 6.5 deg² 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"×4.2" in the final radio continuum map witha median rms noise level of 50 μJy/beam. We identify 1389 radio sources in the field with peak S/N ≥ 5 and present the catalogue ofobserved parameters. We find that 305 sources are resolved, of which 77 consist of multiple radio components. These number countsare in agreement with those found for the COSMOS-VLA 1.4 GHz survey. We derive spectral indices by a comparison with theSydney University Molongolo Sky Survey (SUMSS) 843 MHz 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 deg² southern XXL field. When complete, the survey will provide a unique resource of sensitive, wide-field radio continuum imaging withcomplementary X-ray data in the field. This will facilitate studies of the physical mechanisms of radio-loud and radio-quiet AGNsand galaxy clusters, and the role they play in galaxy evolution. The source catalogue is publicly available online via the XXL MasterCatalogue browser and the Centre de Données astronomiques de Strasbourg (CDS).