The XMM-LSS survey

Free access article

Issue		A&A Volume 423, Number 1, August III 2004


Page(s)		75 - 85
Section		Cosmology (including clusters of galaxies)
DOI		http://dx.doi.org/10.1051/0004-6361:20040162

A&A 423, 75-85 (2004)
DOI: 10.1051/0004-6361:20040162

First high redshift galaxy clusters: Relaxed and collapsing systems

I. Valtchanov^{1, 2}, M. Pierre¹, J. Willis³, S. Dos Santos¹, L. Jones⁴, S. Andreon⁵, C. Adami⁶, B. Altieri⁷, M. Bolzonella⁸, M. Bremer⁹, P.-A. Duc¹, E. Gosset¹⁰, C. Jean¹⁰ and J. Surdej¹⁰

¹ CEA/Saclay, Service d'Astrophysique, 91191, Gif-sur-Yvette, France
e-mail: i.valtchanov@imperial.ac.uk
² Astrophysics Group, Blackett Laboratory, Imperial College, London SW7 2BW, UK
³ ESO, Ave. Alonso de Cordova 3107, Casilla 19, Santiago 19001, Chile
⁴ School of Physics and Astronomy, University of Birmingham, Birmingham, UK
⁵ INAF - Osservatorio Astronomico di Brera, via Brera 28, 20121 Milano, Italy
⁶ LAM, Traverse du Siphon, 13012 Marseille, France
⁷ ESA, Villafranca del Castillo, Spain
⁸ Istituto di Astrofisica Spaziale e Fisica Cosmica, Sezione di Milano, via Bassini 15, 20133 Milano
⁹ Department of Physics, University of Bristol, H.H. Wills Laboratory, Bristol, UK
¹⁰ Université de Liège, Allée du 6 Août, 17, B5C, 4000 Sart Tilman, Belgium

(Received 2 May 2003 / Accepted 5 May 2004)

Abstract
We present five newly found galaxy clusters at z>0.6 from the XMM Large-Scale Structure Survey (XMM-LSS). All five objects are extended X-ray sources in the XMM images. For three of them we have sufficient spectroscopically confirmed member galaxies that an estimate of the velocity dispersion is possible: XLSSC 001 at z=0.613 and $\sigma_V=867^{+80}_{-60}$ km s ^-1, XLSSC 002 at z=0.772 and $\sigma_V=524^{+267}_{-116}$ km s ^-1 and XLSSC 003 at z=0.839 and $\sigma_V=780^{+137}_{-75}$ km s ^-1. These three clusters have X-ray bolometric luminosities $L_{\rm X} \sim 1{-}3 \times 10^{44}$ erg s ^-1 and temperatures 2-4 keV, and consequently are less massive than previously known clusters at similar redshifts, but nevertheless they follow the low redshift scaling relations between $L_{\rm X}, T$ and $\sigma_v$ , within the limits of the measurement errors. One of the clusters, XLSSC 004, is detected independently as an overdensity of galaxies of a colour R-z'=1.4 that matches the redshift of the central galaxy z=0.87, although it cannot unambiguously be confirmed by the spectroscopic observations alone. The highest redshift candidate cluster pertaining to this paper, XLSSC 005, is most likely a double cluster complex at a redshift around unity, associated with an extended X-ray source with probable substructure.

Key words: X-rays: galaxies: clusters -- cosmology: large-scale structure of Universe -- surveys

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