The XXL Survey IX. Optical overdensity and radio continuum analysis of a supercluster at z=0.43
Reviewartikel, 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 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.degrees 35x0.degrees 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 x 1 ''.9, and encompasses an area of 41'x41' with rms noise level lower than similar to 20 mu Jy beam(-1). The noise in the central 15'x15' region is approximate to 11 mu Jy 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 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 similar to 0.degrees 6x0.degrees 2on the sky, which corresponds to a physical size of similar to 12x4 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.

galaxies: groups: general

galaxies: clusters: general

radio continuum: galaxies



N. Baran

Sveučilište u Zagrebu

V. Smolcic

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D. Milakovic

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M. Novak

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J. Delhaize

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F. Gastaldello

Istituto nazionale di astrofisica (INAF)

M. E. Ramos-Ceja

Argelander-Institut für Astronomie

F. Pacaud

Argelander-Institut für Astronomie

S. Bourke

California Institute of Technology (Caltech)

C. L. Carilli

National Radio Astronomy Observatory Socorro

S. Ettori

Osservatorio Astronomico Di Bologna

G. Hallinan

California Institute of Technology (Caltech)

Cathy Horellou

Chalmers, Rymd- och geovetenskap, Radioastronomi och astrofysik

E. Koulouridis

Le Commissariat à l’Énergie Atomique et aux Énergies Alternatives (CEA)

L. Chiappetti

Istituto nazionale di astrofisica (INAF)

O. Miettinen

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O. Melnyk

Taras Shevchenko National University of Kyiv

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K. Mooley

California Institute of Technology (Caltech)

M. Pierre

Le Commissariat à l’Énergie Atomique et aux Énergies Alternatives (CEA)

E. Pompei

European Southern Observatory Santiago

E. Schinnerer


Astronomy and Astrophysics

0004-6361 (ISSN) 1432-0746 (eISSN)

Vol. 592 A8


Astronomi, astrofysik och kosmologi


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