Millimeter imaging of submillimeter galaxies in the COSMOS field: redshift distribution^⋆,⋆⋆

¹ ESO ALMA COFUND Fellow  
² European Southern Observatory, Karl-Schwarzschild-Strasse 2, 85748 Garching, Germany
e-mail: vs@astro.uni-bonn.de
³ Argelander-Institute for Astronomy, Auf dem Hügel 71, Bonn, 53121, Germany
⁴ University of Zagreb, Physics Department, Bijenička cesta 32, 10002 Zagreb, Croatia
⁵ European Southern Observatory, Alonso de Córdoba 3107, Vitacura, Casilla 19001, Santiago 19, Chile
⁶ Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, 53121 Bonn, Germany
⁷ Max Planck Institute for Astronomy, Königstuhl 17, 69117 Heidelberg, Germany
⁸ California Institute of Technology, MC 249-17, 1200 East California Boulevard, Pasadena, CA 91125, USA
⁹ IRAM, 300 rue de la piscine, 38406 Saint-Martin d’Hères, France
¹⁰ Max-Planck-Institut für Extraterrestrische Physik, Giessenbachstraße, 85748 Garching, Germany
¹¹ Laboratoire AIM-Paris-Saclay, CEA/DSM/Irfu CNRS Université Paris Diderot, CE-Saclay, pt courrier 131, 91191 Gif-sur-Yvette, France
¹² Institut d’Astrophysique de Paris, UMR 7095 CNRS, Université Pierre et Marie Curie, 98bis boulevard Arago, 75014 Paris, France
¹³ National Radio Astronomy Observatory, PO Box 0, Socorro, NM 87801-0387, USA
¹⁴ INAF – Osservatorio Astronomico di Bologna, via Ranzani 1, 40127 Bologna, Italy
¹⁵ Harvard-Smithsonian Centre for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA
¹⁶ Laboratoire d’Astrophysique de Marseille, Université de Provence, CNRS, BP 8, Traverse du Siphon, 13376 Marseille Cedex 12, France
¹⁷ National Optical Astronomy Observatory, 950 North Cherry Avenue, Tucson, AZ 85719, USA
¹⁸ Institute for Astronomy, ETH Zürich, Wolfgang-Pauli-strasse 27, 8093 Zürich, Switzerland
¹⁹ Institute for Astronomy, University of Hawaii, 2680 Woodlawn Drive, Honolulu, HI, 96822, USA
²⁰ National Radio Astronomy Observatory, 520 Edgemont Road, Charlottesville, VA 22903, USA
²¹ Research Center for Space and Cosmic Evolution, Ehime University, Bunkyo-cho, Matsuyama 790-8577, Japan

Received: 8 April 2012
Accepted: 24 May 2012

Abstract

We present new IRAM Plateau de Bure interferometer (PdBI) 1.3 mm continuum observations at ~1.5′′ resolution of 28 submillimeter galaxies (SMGs), previously discovered with the 870 μm bolometer LABOCA at the APEX telescope from the central 0.7 deg² of the COSMOS field. Nineteen out of the 28 LABOCA sources were detected with PdBI at a ≳3σ level of ≈1.4 mJy/beam. A combined analysis of this new sample with existing interferometrically identified SMGs in the COSMOS field yields the following results: i) ≳15%, and possibly up to ~40% of single-dish detected SMGs consist of multiple sources; ii) statistical analysis of multi-wavelength counterparts to single-dish SMGs shows that only ~50% have real radio or IR counterparts; iii) ~18% of interferometric SMGs have either no multi-wavelength counterpart or only a radio-counterpart; and iv) ~50–70% of z ≳ 3 SMGs have no radio counterparts (down to an rms of 7–12 μJy at 1.4 GHz). Using the exactinterferometric positions to identify the multi-wavelength counterparts allows us to determine accurate photometric redshifts for these sources. The redshift distributions of the combined and the individual 1.1 mm and 870 μm selected samples shows a higher mean and a broader width than those derived in previous studies. This study finds that on average brighter and/or mm- selected SMGs are located at higher redshifts, consistent with previous studies. The mean redshift for the 1.1 mm selected sample ( = 3.1 ± 0.4) is tentatively higher than that for the 870 μm selected sample ( = 2.6 ± 0.4). Based on our nearly complete sample of AzTEC 1.1 mm SMGs in a 0.15 deg² area, we infer a higher surface density of z ≳ 4 SMGs than predicted by current cosmological models. In summary, our findings imply that interferometric identifications at (sub-)millimeter wavelengths are crucial to build statistically complete and unbiased samples of SMGs.