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Published February 2011 | Published
Journal Article Open

A mature cluster with X-ray emission at z = 2.07

Abstract

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 7.2×10^(43) erg sV(-1) and the stellar mass content of the red galaxy population, we estimate a halo mass of 5.3–8×10^(13) 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.

Additional Information

© 2011 ESO. Received 5 November 2010. Accepted 16 November 2010. Published online 11 January 2011. This work is based on data collected at the Subaru Telescope, which is operated by the National Astronomical Observatory of Japan; on observations made with ESO telescopes at the Paranal Observatory, under programmes 072.A-0506 and 381.A-0567; and on observations made with the NASA/ESA Hubble Space Telescope, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555. Support for programme #11174 was provided by NASA through a grant from the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555. Some of the data presented herein were obtained at the W.M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California and the National Aeronautics and Space Administration. We acknowledge funding ERC-StGUPGAL- 240039, ANR-07-BLAN-0228 and ANR-08-JCJC-0008 and Alvio Renzini acknowledges financial support from contract ASI/COFIS I/016/07/0. This work is partially supported by a Grant-in-Aid for Science Research (No.19540245) by the Japanese Ministry of Education, Culture, Sports, Science and Technology. We thank Romain Teyssier for his help with the cosmological calculations, Monique Arnaud, David Elbaz and Piero Rosati for discussions.

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August 22, 2023
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