The Redshift of a Lensing Galaxy in PMN J0134-0931

Abstract

The Sloan Digital Sky Survey (SDSS) automatically targeted as a quasar candidate the recently discovered, gravitationally lensed, extremely reddened z=2.2 quasar PMN J0134-0931. The SDSS spectrum exhibits Ca II absorption at z=0.76451, which we identify as the redshift of a lensing galaxy. Hubble Space Telescope imaging shows that components CDE of the system are significantly redder than components A or B and detects faint galaxy emission between D and A+B. The redshift of the dust responsible for the reddening remains unconstrained with current data. However, we outline a model wherein lensing and differential reddening by a z=0.76451 galaxy pair can entirely explain this system. Detecting mm-wave molecular line absorption from the lensing galaxy or galaxies may be possible in PMN J0134-0931, just as in the lenses PKS1830-211 and B0218+357. Well-constructed optical quasar surveys like the SDSS can contribute to the detection and study of reddened quasars. (Expanded)