Volume 526, February 2011
|Number of page(s)||13|
|Section||Cosmology (including clusters of galaxies)|
|Published online||11 January 2011|
A mature cluster with X-ray emission at z = 2.07
Laboratoire AIM-Paris-Saclay, CEA/DSM-CNRS–Université Paris Diderot,
Irfu/Service d’Astrophysique, CEA Saclay, Orme des Merisiers, 91191
2 Institute for Astronomy, ETH Zürich, Wolfgang-Pauli-strasse 27, 8093 Zürich, Switzerland
3 Max-Planck-Institut für extraterrestrische Physik, Giessenbachstrasse, 85748 Garching, Germany
4 INAF – Osservatorio Astronomico di Padova, Vicolo dell’Osservatorio 5, 35122 Padova, Italy
5 National Astronomical Observatory of Japan, Osawa 2-21-1, Mitaka, Tokyo, Japan
6 Graduate University for Advanced Studies, Osawa 2-21-1, Mitaka, Tokyo, Japan
7 UCO/Lick Observatory, University of California, Santa Cruz, CA 95064, USA
8 Division of Physics, Mathematics and Astronomy, California Institute of Technology, Pasadena, CA 91125, USA
9 Università di Bologna, Dipartimento di Astronomia, via Ranzani 1, 40127 Bologna, Italy
10 National Optical Astronomy Observatory, PO Box 26732, Tucson, AZ 85726, USA
11 Center for Astrophysics, University of Science and Technology of China, Hefei 230026, PR China
12 INAF – Osservatorio Astronomico di Bologna, via Ranzani 1, I 40127 Bologna, Italy
Received: 5 November 2010
Accepted: 16 November 2010
We report evidence of a fully established galaxy cluster at z = 2.07, consisting of a ~20σ overdensity of red, compact spheroidal galaxies spatially coinciding with extended X-ray emission detected with XMM-Newton. We use VLT VIMOS and FORS2 spectra and deep Subaru, VLT and Spitzer imaging to estimate the redshift of the structure from a prominent z = 2.07 spectroscopic redshift spike of emission-line galaxies, concordant with the accurate 12-band photometric redshifts of the red galaxies. Using NICMOS and Keck AO observations, we find that the red galaxies have elliptical morphologies and compact cores. While they do not form a tight red sequence, their colours are consistent with that of a ≳1.3 Gyr population observed at z ~ 2.1. From an X-ray luminosity of 7.2 × 1043 erg s-1 and the stellar mass content of the red galaxy population, we estimate a halo mass of 5.3–8 × 1013 M⊙, comparable to the nearby Virgo cluster. These properties imply that this structure could be the most distant, mature cluster known to date and that X-ray luminous, elliptical-dominated clusters are already forming at substantially earlier epochs than previously known.
Key words: galaxies: clusters: general / galaxies: clusters: individual: CL J1449-0856 / galaxies: high-redshift / large-scale structure of Universe
© ESO, 2011
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