Astronomy & Astrophysics

Free access article

Issue		A&A Volume 424, Number 1, September II 2004
Page(s)		1 - 12
Section		Cosmology (including clusters of galaxies)
DOI		10.1051/0004-6361:20035885

A&A 424, 1-12 (2004)
DOI: 10.1051/0004-6361:20035885

A multi-wavelength study of the proto-cluster surrounding the z = 4.1 radio galaxy TN J1338-1942

C. De Breuck^{1, 2}, F. Bertoldi³, C. Carilli⁴, A. Omont², B. Venemans⁵, H. Röttgering⁵, R. Overzier⁵, M. Reuland^{5, 6, 7}, G. Miley⁵, R. Ivison^{8, 9} and W. van Breugel⁶

¹ European Southern Observatory, Karl Schwarzschild Straße 2, 85748 Garching, Germany
    e-mail: cdebreuc@eso.org
² Institut d'Astrophysique de Paris, CNRS, 98bis boulevard Arago, 75014 Paris, France
    e-mail: omont@iap.fr
³ Max Planck Institut für Radioastronomie, Auf dem Hügel 69, 53121 Bonn, Germany
    e-mail: bertoldi@mpifr-bonn.mpg.de
⁴ National Radio Astronomy Observatory, PO Box O, Socorro, NM 87801, USA
    e-mail: ccarilli@nrao.edu
⁵ Sterrewacht Leiden, Postbus 9513, 2300 RA Leiden, The Netherlands
    e-mail: [venemans;rottgeri;overzier;miley]@strw.leidenuniv.nl
⁶ IGPP/LLNL, L-413, 7000 East Ave, Livermore, CA 94550, USA
    e-mail: [mreuland;wil]@igpp.ucllnl.org
⁷ Department of Physics, University of California, Davis, CA 95616, USA
⁸ Astronomy Technology Centre, Royal Observatory, Blackford Hill, Edinburgh EH9 3HJ, UK
    e-mail: rji@roe.ac.uk
⁹ Institute for Astronomy, University of Edinburgh, Royal Observatory, Blackford Hill, Edinburgh EH9 3HJ, UK

(Received 16 December 2003 / Accepted 10 May 2004 )

Abstract
We present a 1.2 mm (250 GHz) map obtained with MAMBO on the IRAM 30 m telescope of the central 25 arcmin ² of the proto-cluster surrounding the z=4.1 radio galaxy TN J1338-1942. The map reaches a 1 $\sigma$ sensitivity of 0.6 mJy in the central area, increasing to 1.2 mJy at the edges. We detect 10 candidate mm sources, of which 8 are also detected in a deep VLA 1.4 GHz map and/or a VLT R-band image. Three sources have a flux density $S_{\rm 1.2~mm}>4.0$ mJy, representing a 7 $\sigma$ overdensity compared to random field surveys, which predict only 1 such source in our map area. We obtained SCUBA/JCMT 850 $\mu$ m and 450 $\mu$ m photometry of six radio/optically identified MAMBO sources, confirming 5 of them with ${\it {\it S/N}} >4$ . Radio-to-mm and mm-to-submm redshift estimators cannot put strong constraints on the redshifts of these MAMBO sources, but 9 of them are consistent within the uncertainties (mean $\Delta z=+2.6$ ) with z=4.1. One faint MAMBO source is possibly identified with an extremely red object ( R-K=6.1) at a likely spectroscopic redshift z=1.18. The four brightest MAMBO sources are all located north of the radio galaxy, while the densest area of companion Ly $\alpha$ excess and Lyman break galaxies is to the southeast. None of the 14 spectroscopically confirmed Ly $\alpha$ emitters in the MAMBO field are detected at 1.2 mm; their average 1.2 mm flux density is $\langle S_{\rm 1.2~mm}\rangle=0.25\pm0.24$ mJy. If the mm sources lie at z=4.1, none of them show excess Ly $\alpha$ emission in our narrow-band images. Both populations thus show no apparent overlap, possibly due to dust quenching the Ly $\alpha$ emission. If the mm sources are part of the proto-cluster, our results suggest that galaxies with star formation rates of a few 1000 $M_{\odot}$ yr ^-1 could be spread throughout the proto-cluster over projected scales of at least 2 Mpc.

Key words: galaxies: individual: TN J1338-1942 -- galaxies: clusters: individual: TN J1338-1942 -- galaxies: formation -- cosmology: observations

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