Cosmic Alignment toward the Radio Einstein Ring PKS 1830-211?

Optical and near-IR Hubble Space Telescope and Gemini North adaptive optics images, further improved through deconvolution, are used to explore the gravitationally lensed radio source PKS 1830-211. The line of sight to the quasar at z=2.507 appears to be very busy, with the presence, within 0.5" from the source, of (1) a possible galactic main-sequence star, (2) a faint red lensing galaxy visible only in H band, and (3) a new object whose colors and morphology match those of an almost face-on spiral. The V-I color and faint I magnitude of the latter suggest that it is associated with the molecular absorber seen toward PKS 1830-211, at z=0.89 rather than with the z=0.19 H I absorber previously reported in the spectrum of PKS 1830-211. While this discovery might ease the interpretation of the observed absorption lines, it also complicates the modeling of the lensing potential well, hence decreasing the interest in using this system as a means to measure H₀ through the time delay between the lensed images. This is the first case of a quasar lensed by an almost face-on spiral galaxy. Based on observations made with the NASA/ESA Hubble Space Telescope, obtained from the Data Archive at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555. The HST data used here come from the archives related to the programs 7495, 8804, and 9133 (CASTLES). This study is also based on observations made with the NOAO Gemini North Telescope; NOAO is operated by the Association of Universities for Research in Astronomy (AURA), Inc., under cooperative agreement with the National Science Foundation.