* Astronomy

Title: A bright z=5.2 lensed submillimetre galaxy in the field of Abell 773: HLSJ091828.6+514223
Authors: F. Combes (Obs-Paris), M. Rex (Tucson), T. D. Rawle (Tucson), E. Egami (Tucson), F. Boone (Toulouse), I. Smail (Durham), J. Richard (Lyon), R.J. Ivison (Edinburgh), M. Gurwell (Harvard), C.M. Casey (Hawaii), A. Omont (IAP-Paris), A. Berciano Alba (ASTRON), M. Dessauges-Zavadsky (Geneva), A.C. Edge (Durham), G.G. Fazio (Harvard), J-P. Kneib (Marseille), N. Okabe (Taipei), R. Pello (Toulouse), P. G. Perez-Gonzalez (Madrid), D. Schaerer (Geneva), G.P. Smith (Birmingham), A.M. Swinbank (Durham), P. van der Werf (Leiden)

During our Herschel Lensing Survey (HLS) of massive galaxy clusters, we have discovered an exceptionally bright submillimetre source, behind the z=0.22 cluster Abell 773, which appears to be a strongly lensed submillimetre galaxy (SMG) at z=5.2429. This source is unusual compared to most other lensed sources discovered by Herschel so far, both for its higher submm flux (~ 200mJy at 500micron) and its high redshift. The dominant lens is a foreground z=0.63 galaxy, not the cluster itself. From the continuum detected, we derive a far-infrared luminosity of LFIR= 1.1E14 /\mu Lo, where \mu is the magnification factor, likely ~ 11. We report here the redshift identification through CO lines with the IRAM-30m, 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) detected with the EVLA. All lines decompose in a wide and strong red component, and a narrower and weaker blue component, 540\kms apart. Assuming the local ULIRG CO-to-H2 conversion ratio, the H2 mass derived is 5.8E11/\mu Mo, of which one third is contained in a cool component. From the CI line we derive a CI/H2 number abundance of 0.6E-4 similar to that in other ULIRGs. We detect the water line, with an intensity ratio I(H2O)/I(CO) ~ 0.5, suggesting a strong local FIR radiation field, possibly from an AGN component. The water line is strong only in the red velocity component. We detect for the first time at high-z the [NII]205micron line. It shows comparable blue and red components, with a strikingly broad blue one, suggesting strong ionised gas flows.

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