A Keck Survey of Gravitational Lens Systems. I. Spectroscopy of SBS 0909+532, HST 1411+5211, and CLASS B2319+051

We present new results from a continuing Keck program to study gravitationallens systems. We have obtained redshifts for three lens systems, SBS 0909+532,HST 1411+5211, and CLASS B2319+051. For all of these systems, either the sourceor lens redshift (or both) has been previously unidentified. We find (z_l, z_s)= (0.830, 1.377) for SBS 0909+532; (z_l, z_s) = (0.465, 2.811) for HST1411+5211, although the source redshift is still tentative; and (z_l1, z_l2) =(0.624, 0.588) for the two lensing galaxies in CLASS B2319+051. The backgroundradio source in B2319+051 has not been detected optically; its redshift is,therefore, still unknown. We find that the spectral features of the centrallensing galaxy in all three systems are typical of an early-type galaxy. Theobserved image splittings in SBS 0909+532 and HST 1411+5211 imply that themasses within the Einstein ring radii of the lensing galaxies are 1.4 x 10^{11}and 2.0 x 10^{11} h^{-1} M_sun, respectively. The resulting B bandmass-to-light ratio for HST 1411+5211 is 41.3 +/- 1.2 h (M/L)_sun, a factor of5 times higher than the average early-type lensing galaxy. This largemass-to-light is almost certainly the result of the additional masscontribution from the cluster CL 3C295 at z = 0.46. For the lensing galaxy inSBS 0909+532, we measure (M/L)_B = 4^{+11}_{-3} h (M/L)_sun where the largeerrors are the result of significant uncertainty in the galaxy luminosity.While we cannot measure directly the mass-to-light ratio of the lensing galaxyin B2319+051, we estimate that (M/L)_B is between 3-7 h (M/L)_sun.Comment: Accepted for publication in Astronomical Journal. 21 pages, including 7 figure