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 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).
