A&A 505, L9-L12 (2009)
DOI: 10.1051/0004-6361/200912929

Letter

The spectroscopically confirmed huge cosmic structure at z = 0.55

M. Tanaka¹, A. Finoguenov^{2, 3}, T. Kodama⁴, Y. Koyama⁵, B. Maughan⁶, and F. Nakata<sup>7

1</sup>  European Southern Observatory, Karl-Schwarzschild-Str. 2, 85748 Garching bei München, Germany
    e-mail: mtanaka@eso.org
²  Max-Planck-Institut für extraterrestrische Physik, Giessenbachstrasse, 85748 Garching bei München, Germany
³  University of Maryland, Baltimore County, 1000 Hilltop Circle, Baltimore, MD 21250, USA
⁴  National Astronomical Observatory of Japan, Mitaka, Tokyo 181-8588, Japan
⁵  Department of Astronomy, School of Science, University of Tokyo, Tokyo 113–0033, Japan
⁶  HH Wills Physics Laboratory, Tyndall Avenue, Bristol, BS8 1TL, UK
⁷  Subaru Telescope, National Astronomical Observatory of Japan, 650 North A'ohoku Place, Hilo, HI 96720, USA

Received 20 July 2009 / Accepted 2 September 2009

Abstract
We report on the spectroscopic confirmation of a huge cosmic structure around the CL0016 cluster at z=0.55. We made wide-field imaging observations of the surrounding regions of the cluster and identified more than 30 concentrations of red galaxies near the cluster redshift. The follow-up spectroscopic observations of the most prominent part of the structure confirmed 14 systems close to the cluster redshift, roughly half of which have a probability of being bound to the cluster dynamically. We also made an X-ray follow-up, which detected extended X-ray emissions from 70% of the systems in the X-ray surveyed region. The observed structure is among the richest ever observed in the distant Universe. They will be an ideal site for quantifying environmental variations in the galaxy properties and effects of large-scale structure on galaxy evolution.

Key words: galaxies: clusters: individual: CL0016+16 -- large-scale structure of Universe

© ESO 2009

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