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

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 arcmin² of the proto-cluster surrounding the radio galaxy TN J1338-1942. The map reaches a 1σ 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  mJy, representing a 7σ overdensity compared to random field surveys, which predict only 1 such source in our map area. We obtained SCUBA/JCMT 850 μm and 450 μm photometry of six radio/optically identified MAMBO sources, confirming 5 of them with . 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 ) with . One faint MAMBO source is possibly identified with an extremely red object () at a likely spectroscopic redshift . The four brightest MAMBO sources are all located north of the radio galaxy, while the densest area of companion Lyα excess and Lyman break galaxies is to the southeast. None of the 14 spectroscopically confirmed Lyα emitters in the MAMBO field are detected at 1.2 mm; their average 1.2 mm flux density is  mJy. If the mm sources lie at , none of them show excess Lyα emission in our narrow-band images. Both populations thus show no apparent overlap, possibly due to dust quenching the Lyα emission. If the mm sources are part of the proto-cluster, our results suggest that galaxies with star formation rates of a few 1000  yr^-1 could be spread throughout the proto-cluster over projected scales of at least 2 Mpc.