Keck Spectroscopy of Three Gravitational Lens Systems Discovered in the JVAS and CLASS Surveys

We present spectra of three gravitational lens systems taken with the Low Resolution Imaging Spectrograph on the W. M. Keck telescopes. All of the systems were discovered in the JVAS and CLASS radio surveys, which were designed to nd lenses suitable for measuring Previous spectra of these H 0 . systems had low signal-to-noise ratios, and only one of the source redshifts was secure. Our observations provide unambiguous lens and source redshifts for all of the systems, with 1.339), (z l , z s ) \ (0.4060, (0.5990, 1.535), and (0.4144, 1.589) for B0712]472, B1030]074, and B1600]434, respectively. The observed image splittings in the systems imply that the masses of the lensing galaxies within their Einstein rings are 5.4 ] 1010, 1.2 ] 1011, and 6.3 ] 1010 h~1