The XXL Survey. VII. A supercluster of galaxies at z = 0.43

Pompei, E. and Adami, C. and Eckert, D. and Gastaldello, F. and Lavoie, S. and Poggianti, B. and Altieri, B. and Alis, S. and Baran, Nikola and Benoist, C. and Jaffe, Y. L. and Koulouridis, E. and Maurogordato, S. and Pacaud, F. and Pierre, M. and Sadibekova, T. and Smolčić, Vernesa and Valtchanov, I. (2016) The XXL Survey. VII. A supercluster of galaxies at z = 0.43. Astronomy and Astrophysics, 592. Art. No. A6. ISSN 0004-6361

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Context. The XXL Survey is the largest homogeneous and contiguous survey carried out with XMM-Newton. Covering an area of 50 deg2 distributed over two fields, it primarily investigates the large-scale structures of the Universe using the distribution of galaxy clusters and active galactic nuclei as tracers of the matter distribution. Aims. Given its depth and sky coverage, XXL is particularly suited to systematically unveiling the clustering of X-ray clusters and to identifying superstructures in a homogeneous X-ray sample down to the typical mass scale of a local massive cluster. Methods. A friends-of-friends algorithm in three-dimensional physical space was run to identify large-scale structures. In this paper we report the discovery of the highest redshift supercluster of galaxies found in the XXL Survey. We describe the X-ray properties of the clusters members of the structure and the optical follow-up. Results. The newly discovered supercluster is composed of six clusters of galaxies at a median redshift z ∼ 0.43 and distributed across ∼300×150 (10×5 Mpc) on the sky. This structure is very compact with all the clusters residing in one XMM pointing; for this reason this is the first supercluster discovered with the XXL Survey. Photometric redshifts from the CFHTLS (Canada-France-Hawaii Telescope Legacy Survey) data release T0007 placed the supercluster at an approximate redshift of zphot ∼ 0.45; subsequent spectroscopic follow-up with WHT (William Herschel Telescope) and NTT (New Technology Telescope) confirmed a median redshift of z ∼ 0.43. An estimate of the X-ray mass and luminosity of this supercluster returns values of 1.7 × 1015 M and of 1.68 × 1044 erg s−1 , respectively, and a total gas mass of Mgas = 9.3 × 1013 M . These values put XLSSC-e at the average mass range of superclusters; its appearance, with two members of equal size, is quite unusual with respect to other superclusters and provides a unique view of the formation process of a massive structure.

Item Type: Article
Keywords: galaxies: clusters: general; X-rays: galaxies: clusters
Date: 15 June 2016
Subjects: NATURAL SCIENCES > Physics > Astronomy and Astrophysics
Additional Information: © ESO 2016. Received 7 August 2015. Accepted 27 October 2015. Published online 15 June 2016.
Divisions: Faculty of Science > Department of Physics
Publisher: EDP Sciences
Depositing User: Vernesa Smolčić
Date Deposited: 26 Mar 2017 16:03
Last Modified: 29 Nov 2017 16:45

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