SIMBAD references

We present observations with the Karl G. Jansky Very Large Array (VLA) at 3GHz (10 cm) toward a sub-field of the XXL-North 25deg² field targeting the first supercluster discovered in the XXL Survey. The structure has been found at a spectroscopic redshift of 0.43 and extending over 0.35x0.1 on the sky. The aim of this paper is twofold. First, we present the 3GHz VLA radio continuum observations, the final radio mosaic and radio source catalogue, and, second, we perform a detailed analysis of the supercluster in the optical and radio regimes using photometric redshifts from the CFHTLS survey and our new VLA-XXL data. Our final 3GHz radio mosaic has a resolution of 3.2x1.9, and encompasses an area of 41'x41' with rms noise level lower than ∼20µJy/beam. The noise in the central 15'x15' region is ~=11µJy/beam. From the mosaic we extract a catalogue of 155 radio sources with signal-to-noise ratio (S/N)≥6, eight of which are large, multicomponent sources, and 123 (79%) of which can be associated with optical sources in the CFHTLS W1 catalogue. Applying Voronoi tessellation analysis (VTA) in the area around the X-ray identified supercluster using photometric redshifts from the CFHTLS survey we identify a total of seventeen overdensities at z_phot=0.35-0.50, 7 of which are associated with clusters detected in the XMM-Newton XXL data. We find a mean photometric redshift of 0.43 for our overdensities, consistent with the spectroscopic redshifts of the brightest cluster galaxies of seven X-ray detected clusters. The full VTA-identified structure extends over ∼0.6x0.2 on the sky, which corresponds to a physical size of ∼12x4Mpc² at z=0.43. No large radio galaxies are present within the overdensities, and we associate eight (S/N>7) radio sources with potential group/cluster member galaxies. The spatial distribution of the red and blue VTA-identified potential group member galaxies, selected by their observed g-r colours, suggests that the clusters are not virialised yet, but are dynamically young, as expected for hierarchical structure growth in a ΛCDM universe. Further spectroscopic data are required to analyse the dynamical state of the groups.