Keck spectroscopy of Cosmic Lens All-Sky Survey gravitational lenses

J. P. McKean, L. V E Koopmans, I. W A Browne, C. D. Fassnacht, R. D. Blandford, L. M. Lubin, A. C S Readhead

    Research output: Contribution to journalArticlepeer-review


    We present the optical spectra of four newly discovered gravitational lenses from the Cosmic Lens All-Sky Survey (CLASS). These observations were carried out using the Low-Resolution Imaging Spectrograph on the W. M. Keck-I Telescope as part of a programme to study galaxy-scale gravitational lenses. From our spectra, we found the redshift of the background source in CLASS B0128+437 (Zs = 3.1240 ± 0.0042) and the lensing galaxy redshifts in CLASS B0445+123 (z1 = 0.5583 ± 0.0003) and CLASS B0850+054 (z1 = 0.5883 ± 0.0006). Intriguingly, we also discovered that CLASS B0631+519 may have two lensing galaxies (z1,1 = 0.0896 ± 0.0001, z1,2 = 0.6196 ± 0.0004). We also found a single unidentified emission line from the lensing galaxy in CLASS B0128+437 and the lensed source in CLASS B0850+054. We find the lensing galaxies in CLASS B0445+123 and CLASS B0631+519 (1, 2) to be early-type galaxies with Einstein radii of 2.8-3.0 h-1 kpc. The deflector in CLASS B0850+054 is a late-type galaxy with an Einstein radius of 1.6 h-1 kpc.
    Original languageEnglish
    Pages (from-to)167-174
    Number of pages7
    JournalMonthly Notices of the Royal Astronomical Society
    Issue number1
    Publication statusPublished - 1 May 2004


    • Gravitational lensing
    • Quasars: individual: CLASS B0128+437
    • Quasars: individual: CLASS B0445+123
    • Quasars: individual: CLASS B0631+519
    • Quasars: individual: CLASS B0850+054


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