The Einstein Ring GAL-CLUS-022058s: a Lensed Ultrabright Submillimeter Galaxy at z = 1.4796

We report an ultrabright lensed submillimeter galaxy at z_spec = 1.4796, identified as a result of a full-sky cross-correlation of the AllWISE and Planck compact source catalogs aimed at searching for bright submillimeter galaxies at z ~ 1.5-2.8. Atacama Pathfinder Experiment (APEX)/LABOCA observations of the candidate galaxy reveal a source with flux S_870μm = 54 ± 8 mJy. The position of the APEX source coincides with the position of the AllWISE mid-IR source and with the Einstein ring GAL-CLUS-022058s, observed with the Hubble Space Telescope. Archival VLT/FORS observations reveal the redshift of this Einstein ring, z_spec = 1.4796, and the detection of the CO(5-4) line at z_spec = 1.4802 with APEX/nFLASH230 confirms the redshift of the submillimeter emission. The lensed source appears to be gravitationally magnified by a massive foreground galaxy cluster lens at z = 0.36. We use Lenstool to model the gravitational lensing, which is close to a "fold arc" configuration for an elliptical mass distribution of the central halo, where four images of the lensed galaxy are seen; the mean magnification is μ_L = 18 ± 4. We have determined an intrinsic rest-frame infrared luminosity of L_IR ≈10¹²L_⊙ and a likely star formation rate of ~70-170 M_⊙yr^-1. The molecular gas mass is M_mol ~ 2.6 × 10¹⁰M_⊙ and the gas fraction is f = 0.34 ± 0.07. We also obtain a stellar mass log (M_*/M_⊙) = 10.7 ± 0.1 and a specific star formation rate log (sSFR/Gyr^-1) = 0.15 ± 0.03. This galaxy lies on the so-called main sequence of star-forming galaxies at this redshift.