Spectra of the RXS J1131-1231 lensing system

The spectra of two of the star-like images in the gravitational lens system RXS J1131-1231 (labeled A and D in the top panel) are very similar and are therefore from the same object, i.e., the lensed quasar. The emission lines identified in these spectra are typical of a quasar and the redshft is measured as z = 0.66. The bottom panel shows the spectrum of the lensing, elliptical galaxy at redshift z=0.3.