2009ApJ...692..694G

We report the serendipitous discovery of an Einstein Ring in the optical band from the Sloan Digital Sky Survey (SDSS) data and four associated images of a background source. The lens galaxy appears to be a nearby dwarf spheroid at a redshift of 0.0375±0.002. The lensed quasar is at a redshift of 0.6842 ±0.0014, and its multiple images are distributed almost 360° around the lens nearly along a ring of radius ∼6".0. Single-component lens models require a mass of the galaxy of almost 10¹² M_☉ within 6".0 from the lens center. With the available data, we are unable to determine the exact positions, orientations, and fluxes of the quasar and the galaxy, though there appears to be evidence for a double- or multiple-merging image of the quasar. We have also detected strong radio and X-ray emissions from this system. It is indicative that this ring system may be embedded in a group or cluster of galaxies. This unique ring, by virtue of the closeness of the lens galaxy, offers a possible probe of some key issues such as the mass-to-light ratio of intrinsically faint galaxies and the existence of large-scale magnetic fields in elliptical galaxies.