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Published August 2007 | Published
Journal Article Open

The Gravitational Lens-Galaxy Group Connection. II. Groups Associated with B2319+051 and B1600+434


We report on the results of a spectroscopic survey of the environments of the gravitational lens systems CLASS B1600+434 (z_l = 0.41, z_s = 1.59) and CLASS B2319+051 (z_l = 0.62). The B1600+434 system has a time delay measured for it, and we find that the system lies in a group with a velocity dispersion of 90 km s^(-1) and at least seven members. B2319+051 has a large group in its immediate foreground with at least 10 members and a velocity dispersion of 460 km s^(-1) and another in the background of the lens with a velocity dispersion of 190 km s^(-1). These systems increase the sample of spectroscopically confirmed groups associated with strong lenses by 20%. We find that modeling groups as single group-sized halos produces only small corrections (κ_(env,grp) ~ 0.01) to lensing models. However, the very local environments, i.e., galaxies within ~15" of the lensing galaxy, have stronger effects on the lens models of the systems studied here. We quantify the effects of the local environment on the lens models and find up to an ≈10% correction to the derived value of H_0 for B1600+434 compared to models that do not account for the lens environment.

Additional Information

© 2007 The American Astronomical Society. Received 2006 March 16; accepted 2007 April 27. Based in part on observations made with the NASA/ESA Hubble Space Telescope, obtained from the Data Archive at the Space Telescope Science Institute (STScI). STScI is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS5-26555. These observations are associated with program AR-10300, supported by NASA through a grant from STScI. In addition, some of the data presented herein were obtained at the W. M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California, and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W. M. Keck Foundation. The authors wish to recognize and acknowledge the very significant cultural role and reverence that the summit of Mauna Kea has always had within the indigenous Hawaiian community. We are most fortunate to have the opportunity to conduct observations from this mountain. This work is also based in part on data collected at the Subaru Telescope and obtained from the SMOKA science archive at the Astronomical Data Analysis Center, which are operated by the National Astronomical Observatory of Japan. Part of this work was supported by the European Community's Sixth Framework Marie Curie Research Training Network Programme, Contract No. MRTN-CT-2004-505183 "ANGLES."

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August 22, 2023
October 19, 2023