Hyman, Sóley ÓWilkes, Belinda J.Willner, S. P.Kuraszkiewicz, JoannaAzadi, MojeganWorrall, D. M.Foord, AdiVegetti, SimonaAshby, Matthew L. N.Birkinshaw, MarkFassnacht, ChristopherHaas, MartinStern, Daniel2024-08-202024-08-202024-07-30https://doi.org/10.48550/arXiv.2407.21020http://hdl.handle.net/11603/35745The 3C 220.3 system is a rare case of a foreground narrow-line radio galaxy (“galaxy A,” zₐ = 0.6850) lensing a background submillimeter galaxy (zₛₘG₁ = 2.221). New spectra from MMT/Binospec confirm that the companion galaxy (“galaxy B”) is part of the lensing system with zB = 0.6835. New threecolor HST data reveal a full Einstein ring and allow a more precise lens model. The new HST images also reveal extended emission around galaxy A, and the spectra show extended [O II] emission with irregular morphology and complex velocity structure. All indications are that the two lensing galaxies are a gravitationally interacting pair. Strong [O II] emission from both galaxies A and B suggests current star formation, which could be a consequence of the interaction. This would indicate a younger stellar population than previously assumed and imply smaller stellar masses for the same luminosity. The improved lens model and expanded spectral energy distributions have enabled better stellar-mass estimates for the foreground galaxies. The resulting dark matter fractions are ~0.8, higher than previously calculated. Deeper Chandra imaging shows extended X-ray emission but no evidence for a point X-ray source associated with either galaxy. The detection of X-rays from the radio lobes of 3C 220.3 allows an estimate of ~3 nT for the magnetic fields in the lobes, a factor of ~3 below the equipartition fields, as typical for radio galaxies.23 pagesen-USAstrophysics - Astrophysics of GalaxiesText