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Issue A&A
Volume 428, Number 3, December IV 2004
Page(s) 793 - 815
Section Cosmology (including clusters of galaxies)
DOI http://dx.doi.org/10.1051/0004-6361:20040075



A&A 428, 793-815 (2004)
DOI: 10.1051/0004-6361:20040075

A search for clusters at high redshift

III. Candidate H $\alpha$ emitters and EROs in the PKS 1138-262 proto-cluster at z = 2.16
J. D. Kurk1, L. Pentericci2, H. J. A. Röttgering1 and G. K. Miley1

1  Sterrewacht Leiden, PO Box 9513, 2300 RA Leiden, The Netherlands
    e-mail: kurk@arcetri.astro.it
2  Max-Planck-Institut für Astronomie, Königstuhl 17, 69117 Heidelberg, Germany

(Received 21 January 2003 / Accepted 19 February 2004)

Abstract
In this paper we present deep VLT multi wavelength imaging observations of the field around the radio galaxy PKS 1138-262 aimed at detecting and studying a (potential) proto-cluster centered at this radio source. PKS 1138-262 is a massive galaxy at z = 2.16, located in a dense environment as indicated by optical, X-ray and radio observations. We had already found an over-density of Ly $\alpha$ emitting galaxies in this field, consistent with a proto-cluster structure associated with the radio galaxy. In addition, we find 40 candidate H $\alpha$ emitters that have nominal rest frame equivalent width >25 Å within 1.8 Mpc and 2000 km s -1 of the radio galaxy. Furthermore, we find 44 objects with I - K > 4.3. This number of extremely red objects (EROs) is about twice the number found in blank field ERO surveys, suggesting that some EROs in this field are part of the proto-cluster. The density of H $\alpha$ emitters and extremely red objects increases towards the radio galaxy, indicating a physical association. From comparisons with other K band, ERO, H $\alpha$ and Ly $\alpha$ surveys, we conclude that PKS 1138-262 is located in a density peak which will evolve into a cluster of galaxies.


Key words: galaxies: active -- galaxies: clusters: general -- galaxies: evolution -- cosmology: observations -- cosmology: early Universe

SIMBAD Objects



© ESO 2004

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