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Published February 2000 | Published + Accepted Version
Journal Article Open

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 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 (M/L) 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 ratio is almost certainly the result of the additional mass contribution from the cluster CL 3C 295 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 t_he 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)_⊙.

Additional Information

© 2000 The American Astronomical Society. Received 1999 September 22; accepted 1999 October 25. We would like to thank the referee, Emilio Falco, for very useful comments on the text. We thank Mark Metzger, Gordon Squires, and Chuck Steidel for helpful discussions and essential material aids to this paper. The W. M. Keck Observatory is operated as a scientific partnership among the California Institute of Technology, the University of California, and the National Aeronautics and Space Administration. It was made possible by the generous financial support of the W. M. Keck Foundation. MERLIN is operated as a national facility by the Nuffield Radio Astronomy Laboratories, University of Manchester, on behalf of the UK Particle Physics and Astronomy Research Council. Support for L. M. L. was provided by NASA through Hubble Fellowship grant HF-01095.01-97A awarded by the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., for NASA under contract NAS 5-26555. This work was partially supported by NSF under grant AST 94-20018.

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Published - Lubin_2000_AJ_119_451.pdf

Accepted Version - 9910523.pdf


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