Volume 538, February 2012
|Number of page(s)||5|
|Published online||09 February 2012|
A bright z = 5.2 lensed submillimeter galaxy in the field of Abell 773
1 Observatoire de Paris, LERMA, CNRS, 61 Av. de l’Observatoire, 75014 Paris, France
2 Steward Observatory, University of Arizona, 933 North Cherry Avenue, Tucson, AZ, 85721, USA
3 Université de Toulouse, UPS-OMP, CNRS, IRAP, 9 Av. colonel Roche, BP 44346, 31028 Toulouse Cedex 4, France
4 Institute for Computational Cosmology, Durham University, South Road, Durham, DH1 3LE, UK
5 CRAL, Université Lyon-1, 9 Av. Charles André, 69561 St Genis Laval, France
6 UK Astronomy Technology Centre, Royal Observatory, Blackford Hill, Edinburgh, EH9 3HJ, UK
7 Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA
8 Institute for Astronomy, University of Hawaii, 2680 Woodlawn Dr, Honolulu, HI 96822, USA
9 Institut d’Astrophysique de Paris, UPMC and CNRS, 98bis Bd. Arago, 75014 Paris, France
10 ASTRON, PO Box 2, 2990 AA Dwingeloo, The Netherlands
11 Geneva Observatory, Université de Genève, 51 chemin des Maillettes, 1290 Versoix, Switzerland
12 LAM, CNRS – Université Aix-Marseille, 38 rue F. Joliot-Curie, 13388 Marseille Cedex 13, France
13 Academia Sinica Institute of Astronomy and Astrophysics (ASIAA), PO Box 23-141, 10617 Taipei, Taiwan
14 Dep. de Astrofisica, Facultad de CC. Fisicas, Universidad Complutense de Madrid, 28040 Madrid, Spain
15 School of Physics and Astronomy, University of Birmingham, Edgbaston, Birmingham B15 2TT, UK
16 Leiden Observatory, Leiden University, PO Box 9513, 2300 RA Leiden, The Netherlands
Received: 28 December 2011
Accepted: 16 January 2012
During our Herschel Lensing Survey (HLS) of massive galaxy clusters, we have discovered an exceptionally bright source behind the z = 0.22 cluster Abell 773, which appears to be a strongly lensed submillimeter galaxy (SMG) at z = 5.2429. This source is unusual compared to most other lensed sources discovered by Herschel so far, because of its higher submm flux (~200 mJy at 500 μm) and its high redshift. The dominant lens is a foreground z = 0.63 galaxy, not the cluster itself. The source has a far-infrared (FIR) luminosity of LFIR = 1.1 × 1014/μ L⊙, where μ is the magnification factor, likely ~11. We report here the redshift identification through CO lines with the IRAM-30 m, and the analysis of the gas excitation, based on CO(7–6), CO(6–5), CO(5–4) detected at IRAM and the CO(2–1) at the EVLA. All lines decompose into a wide and strong red component, and a narrower and weaker blue component, 540 km s-1 apart. Assuming the ultraluminous galaxy (ULIRG) CO-to-H2 conversion ratio, the H2 mass is 5.8 × 1011/μ M⊙, of which one third is in a cool component. From the C I(3P2-3P1) line we derive a C I/H2 number abundance of 6 × 10-5 similar to that in other ULIRGs. The H2Op(2,0,2−1,1,1) line is strong only in the red velocity component, with an intensity ratio I(H2O)/I(CO) ~ 0.5, suggesting a strong local FIR radiation field, possibly from an active nucleus (AGN) component. We detect the [NII]205 μm line for the first time at high-z. It shows comparable blue and red components, with a strikingly broad blue one, suggesting strong ionized gas flows.
Key words: galaxies: evolution / galaxies: high-redshift / galaxies: ISM / infrared: galaxies / submillimeter: galaxies / galaxies: individual: HLSJ091828.6+514223
© ESO, 2012
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