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Resumen:
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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 ?m) 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 L_FIR = 1.1 × 10^14/? L_?, where ? 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-H_2 conversion ratio, the H_2 mass is 5.8×10^11/? M_?, of which one third is in a cool component. From the CI(^3P_2?^3 P_1) line we derive a C_I/H_2 number abundance of 6 × 10^?5 similar to that in other ULIRGs. The H_2O_p(2, 0, 2?1, 1, 1) line is strong only in the red velocity component, with an intensity ratio I(H_2O)/I(CO) ? 0.5, suggesting a strong local FIR radiation field, possibly from an active nucleus (AGN) component. We detect the [NII]205 ?m 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.
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