Cosmic Alignment Towards 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 arcsec, from the source of: (i) a possible galactic main-sequence star, (ii) a faint red lensing galaxy visible only in H-band and (iii) a new object whose colors and morphology match those of an almost face-on spiral galaxy. The V - I color and faint I magnitude of the latter suggest that it is associated with the molecular absorber seen towards PKS 1830-211, at z = 0.89 rather than with the z = 0.19 HI 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 mean to measure H ₀ through the time delay between the images. This is the first case of a quasar lensed by an almost face-on spiral.