The Red Radio Ring: a gravitationally lensed hyperluminous infrared radio galaxy at z=2.553 discovered through the citizen science project SpaceWarps

We report the discovery of a gravitationally lensed hyperluminous infrared galaxy (intrinsic LIR≈1013 L⊙) with strong radio emission (intrinsic L1.4 GHz≈1025WHz−1) at z=2.553. The source was identified in the citizen science project SpaceWarpsthrough the visual inspection of tens of thousands of iJKs colour composite images of luminous red galaxies (LRGs), groups and clusters of galaxies and quasars. Appearing as a partial Einstein ring (re≈3 arcsec) around an LRG at z=0.2, the galaxy is extremely bright in the sub-millimetre for a cosmological source, with the thermal dust emission approaching 1 Jy at peak. The redshift of the lensed galaxy is determined through the detection of the CO(3→2) molecular emission line with the Large Millimetre Telescope's Redshift Search Receiver and through [O iii] and Hα line detections in the near-infrared from Subaru/Infrared Camera and Spectrograph. We have resolved the radio emission with high-resolution (300-400 mas) eMERLIN L-band and Very Large Array C-band imaging. These observations are used in combination with the near-infrared imaging to construct a lens model, which indicates a lensing magnification of μ≈10. The source reconstruction appears to support a radio morphology comprised of a compact (