• DOI:10.1086/500403
• Corpus ID: 118982328

Spectroscopic redshifts for seven lens galaxies

@article{Ofek2006SpectroscopicRF,
  title={Spectroscopic redshifts for seven lens galaxies},
  author={Eran O. Ofek and Dan Maoz and Hans-Walter Rix and Christopher S. Kochanek and Emilio E. Falco},
  journal={The Astrophysical Journal},
  year={2006},
  volume={641},
  pages={70-77}
}

• E. Ofek, D. Maoz, +2 authors E. Falco
• Published 16 October 2005
• Physics
• The Astrophysical Journal

The use of gravitationally lensed quasars for cosmological applications and as probes of galaxy structure and evolution requires knowledge about the lens redshift, which is unknown for a large fraction of lenses. We report Very Large Telescope observations of 11 lensed quasars, designed to measure the redshifts of their lens galaxies. We successfully determined the redshifts for seven systems, five of which were previously unknown. The securely measured redshifts for the lensing galaxies are: HE 0047� 1756 z ¼ 0:408; PMN J0134� 0931 z ¼ 0:766; HE 0230� 2130 z ¼ 0:522; HE 0435� 1223 z ¼ 0:455; SDSS 0924+021 z ¼ 0:393; LBQS 1009� 025 z ¼ 0:871; and WFI J2033� 472 z ¼ 0:658, all with uncertainties of 0.001. For four additional systems (BR I0952� 0115, Q1017� 207, Q1355� 2257, and PMN J1632� 003) we estimate tentative redshifts based on some features in their spectra. Subject headingg gravitational lensing — quasars: general — quasars: individual (BR I0952� 0115, HE 0047� 1756, HE 0230� 2130, HE 0435� 1223, LBQS 1009� 025, PMN J0134� 0931, PMN J1632� 003, Q1017� 207, Q1355� 2257, SDSS 0924+021, WFI J2033� 472) Online material: color figures Theroughly90knowngravitationallenssystemsarepowerful tools for studying cosmology, galaxy structure and galaxy evolution. Most systems have been observed with the Hubble Space Telescope (HST) to obtain precise photometry and astrometry, and increasing numbers have time delay measurements, measurements of microlensing variability, and determinations of the velocity dispersion of the lens galaxy. However, about 60% of the systems still lack the most basic parameters needed to use a lens as an astrophysical tool—the lens and/or source redshifts. One important application of the lenses is to study the evolution of galaxy mass-to-light ratios. Gravitational lenses, unlike other samples of galaxies, are selected based on their masses, ratherthantheircolorsorsurfacebrightnesses.Bycombiningthe masses of the lenses, as determined by lensing, with the photometry of thelens galaxies as determined fromHSTimages, itis possible to measure directly the mass-to-light ratio of the lens