We present observations with the Karl G. Jansky Very Large Array ( VLA ) at 3 GHz ( 10 cm ) toward a sub-field of the XXL-North 25 deg ^ { 2 } 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 ^ { \circ } \hbox to 0.0 pt { . } 35 \times 0 ^ { \circ } \hbox to 0.0 pt { . } 1 on the sky .
The aim of this paper is twofold .
First , we present the 3 GHz 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 3 GHz radio mosaic has a resolution of 3 \aas@@fstack { \prime \prime } 2 \times 1 \aas@@fstack { \prime \prime } 9 , and encompasses an area of 41 \arcmin \times 41 \arcmin with rms noise level lower than \sim 20 ~ { } \mu Jy beam ^ { -1 } .
The noise in the central 15 \arcmin \times 15 \arcmin region is \approx 11 \mu Jy beam ^ { -1 } .
From the mosaic we extract a catalogue of 155 radio sources with signal-to-noise ratio ( S/N ) \geq 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 _ { \mathrm { 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 \sim 0 ^ { \circ } \hbox to 0.0 pt { . } 6 \times 0 ^ { \circ } \hbox to 0.0 pt { . } 2 on the sky , which corresponds to a physical size of \sim 12 \times 4 Mpc ^ { 2 } 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 \Lambda CDM universe .
Further spectroscopic data are required to analyse the dynamical state of the groups .