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Galaxy Groups Associated with Gravitational Lenses and $H_0$ from B1608+656

Published online by Cambridge University Press:  15 June 2005

Chris Fassnacht ,
Lori Lubin ,
John McKean ,
Roy Gal ,
Gordon Squires ,
Leon Koopmans ,
Tommaso Treu ,
Roger Blandford  and
David Rusin
Chris Fassnacht
Affiliation:
Department of Physics, UC Davis, 1 Shields Ave., Davis, CA 95616, USA email: [email protected], [email protected], [email protected], [email protected]
Lori Lubin
Affiliation:
Department of Physics, UC Davis, 1 Shields Ave., Davis, CA 95616, USA email: [email protected], [email protected], [email protected], [email protected]
John McKean
Affiliation:
Department of Physics, UC Davis, 1 Shields Ave., Davis, CA 95616, USA email: [email protected], [email protected], [email protected], [email protected]
Roy Gal
Affiliation:
Department of Physics, UC Davis, 1 Shields Ave., Davis, CA 95616, USA email: [email protected], [email protected], [email protected], [email protected]
Gordon Squires
Affiliation:
Spitzer Science Center, California Institute of Technology, Mail Code 220-6, 1200 East California Boulevard, Pasadena, CA 91125, USA email: [email protected]
Leon Koopmans
Affiliation:
Kapteyn Institute, PO Box 800, 9700AV Groningen, The Netherlands email: [email protected]
Tommaso Treu
Affiliation:
Department of Physics and Astronomy, UCLA, Box 951547, Knudsen Hall, Los Angeles, CA 90095, USA email: [email protected]
Roger Blandford
Affiliation:
KIPAC, Stanford University, 2575 Sand Hill Road, Menlo Park, CA 94025, USA email: [email protected]
David Rusin
Affiliation:
Department of Physics and Astronomy, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA email: [email protected]
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Abstract

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Compact groups of galaxies recently have been discovered in association with several strong gravitational lens systems. These groups provide additional convergence to the lensing potential and thus affect the value of $H_0$ derived from the systems. Lens system time delays are now being measured with uncertainties of only a few percent or better. Additionally, vast improvements are being made in incorporating observational constraints such as Einstein ring structures and stellar velocity dispersions into the lens models. These advances are reducing the uncertainties on $H_0$ to levels at which the the effects of associated galaxy groups may contribute significantly to the overall error budget. We describe a dedicated multiwavelength program, using Keck, HST, and Chandra, to find such groups and measure their properties. We present, as a case study, results obtained from observations of the CLASS lens system B1608+656 and discuss the implications for the value of $H_0$ derived from this system.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

Type
Contributed Papers
Information
Proceedings of the International Astronomical Union , Volume 2004 , Issue IAUS225 , July 2004 , pp. 311 - 317
Copyright
© 2004 International Astronomical Union