A QSO plus host system lensed into a 6" Einstein ring by a low redshift galaxy

Abstract

We report the serendipitous discovery of an "Einstein Ring" in the optical band from the Sloan Digital Sky Survey (SDSS) data and associated four images of a background source. The lens galaxy appears to be a nearby dwarf spheroid at a redshift of 0.0375$\pm$0.002. The lensed quasar is at a redshift of 0.6842$\pm$0.0014 and its multiple images are distributed almost 360$^{o}$ around the lens nearly along a ring of radius $\sim$6."0. Single component lens models require a mass of the galaxy of almost 10$^{12}$ M$_{\odot}$ 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 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 possible probe to some of the key issues like mass-to-light ratio of intrinsically faint galaxies, existence of large scale magnetic fields in elliptical galaxies etc.