Volume 592, August 2016
The XXL Survey: First results
|Number of page(s)||15|
|Published online||15 June 2016|
The XXL Survey
1 University of Zagreb, Physics Department, Bijenička cesta 32, 10000 Zagreb, Croatia
2 INAF–IASF Milano, via Bassini 15, 20133 Milano, Italy
3 Argelander-Institut für Astronomie, Auf dem Hügel 71, 53121 Bonn, Germany
4 California Institute of Technology, Department of Astronomy, 1200 East California Boulevard, Pasadena, CA 91125, USA
5 National Radio Astronomy Observatory, PO Box O, Socorro, New Mexico, NM 87801, USA
6 INAF–Osservatorio Astronomico di Bologna, via Ranzani 1, 40127 Bologna, Italy
7 Chalmers University of Technology, Department of Earth and Space Sciences, Onsala Space Observatory, 439 92 Onsala, Sweden
8 Service d’Astrophysique AIM, DSM/IRFU/SAp, CEA-Saclay, 91191 Gif-sur-Yvette, France
9 European Southern Observatory, Alonso de Córdova 3107, Vitacura, 19001 Casilla, Santiago 19, Chile
10 Max Planck Institute for Astronomy, Königstuhl 17, 69117 Heidelberg, Germany
11 Astronomical Observatory, Taras Shevchenko National University of Kyiv, 3 Observatorna St., 04053 Kyiv, Ukraine
Received: 13 July 2015
Accepted: 22 April 2016
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 deg2 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.̊35 × 0.̊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.̋2 × 1.̋9, and encompasses an area of 41′ × 41′ with rms noise level lower than ~ 20 μJy beam-1. The noise in the central 15′ × 15′ region is ≈ 11 μJy beam-1. 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 zphot = 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.̊6 × 0.̊2 on the sky, which corresponds to a physical size of ~ 12 × 4 Mpc2 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.
Key words: catalogs / galaxies: clusters: general / galaxies: groups: general / radio continuum: galaxies
The full catalogue is available as a queryable database table XXL_VLA_15 via the XXL Master Catalogue browser http://cosmosdb.iasf-milano.inaf.it/XXL. A copy of the catalogue and the mosaic are also available at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (184.108.40.206) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?IX/49
A FITS file of the reduced image is only available at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (220.127.116.11) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/592/A8
© ESO, 2016
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