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 gravitational lens 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 source or lens redshift (or both) has been previously unidentified. 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) for 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+051. The background radio source in B2319+051 has not been detected optically; its redshift is, therefore, still unknown. We find that the spectral features of the central lensing galaxy in all three systems are typical of an early-type galaxy. The observed image splittings in SBS 0909+532 and HST 1411+5211 imply that the masses within the Einstein ring radii of the lensing galaxies are 1.4 × 10 11 and 2.0 × 10 11 h −1 M ⊙ , respectively. The resulting B band mass-to-light ratio for HST 1411+5211 is 41.3 ± 1.2 h (M/L) ⊙ , a factor of ∼ 5 times higher than the average early-type lensing galaxy. This large mass-to-light is almost certainly the result of the additional mass contribution from the cluster CL 3C295 at z = 0.46. For the lensing galaxy in SBS 0909+532, we measure (M/L) B = 4 +11 −3 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-light ratio of the lensing galaxy in B2319+051, we estimate that (M/L) B is between 3 − 7 h (M/L) ⊙. Subject headings: distance scale – galaxies: distances and redshifts – gravitational lensing – quasars: individual (SBS 0909+532, HST 1411+5211, and CLASS B2319+051)