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 designed to study gra vitational lens systems. We have obtained redshifts for three lens systems, SBS 0909+532, FIST 1411+5211, and CLASS B2319+051. For all of these system s, either the source or lens redshift (or both) has been previously unident ified. Our observations provide some of these missing redshifts. We find (z (l),z(s)) = (0.830, 1.377) for SBS 0909+532; (z(l),z(s)) = (0.465, 2.811) f or HST 1411+5211, although the source redshift is still tentative; and (z(l ,1),z(l,2)) = (0.624, 0.588) for the two lensing galaxies in CLASS B2319+05 1. The background radio source in B2319+051 has not been detected optically ; its redshift is, therefore, still unknown. We find that the spectral feat ures of the central lensing galaxy in all three systems are typical of an e arly-type galaxy. The observed image splittings in SBS 0909+532 and HST 141 1+5211 imply that the masses within the Einstein ring radii of the lensing galaxies are 1.4 x 10(11) and 2.0 x 10(11) h(-1) M., respectively. The resu lting B-band mass-to-light ratio (M/L) for HST 1411+5211 is 41.3 +/- 1.2 h (M/L)., a factor of similar to 5 times higher than the average early-type l ensing galaxy. This large mass-to-light ratio is almost certainly the resul t of the additional mass contribution from the cluster CL 3C 295 at z = 0.4 6. For the lensing galaxy in SBS 0909+532, we measure (M/L)(B) = 4(-3)(+11) h (M/L)., where the large errors are the result of significant uncertainty in the galaxy luminosity. While we cannot measure directly the mass-to-lig ht ratio of the lensing galaxy in B2319+051, we estimate that (M/L)(B) is b etween 3-7 h (M/L)..