2004MNRAS.350..167M

We present the optical spectra of four newly discovered gravitational lenses from the Cosmic Lens All-Sky Survey (CLASS). These observations were carried out using the Low-Resolution Imaging Spectrograph on the W. M. Keck-I Telescope as part of a programme to study galaxy-scale gravitational lenses. From our spectra, we found the redshift of the background source in CLASS B0128+437 (z_s= 3.1240±0.0042) and the lensing galaxy redshifts in CLASS B0445+123 (z₁= 0.5583±0.0003) and CLASS B0850+054 (z_l= 0.5883±0.0006). Intriguingly, we also discovered that CLASS B0631+519 may have two lensing galaxies (z_l,1= 0.0896±0.0001, z_l,2= 0.6196±0.0004). We also found a single unidentified emission line from the lensing galaxy in CLASS B0128+437 and the lensed source in CLASS B0850+054. We find the lensing galaxies in CLASS B0445+123 and CLASS B0631+519 (l, 2) to be early-type galaxies with Einstein radii of 2.8-3.0 h^–1 kpc. The deflector in CLASS B0850+054 is a late-type galaxy with an Einstein radius of 1.6 h^–1 kpc.