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Published November 10, 2006 | Published + Submitted
Journal Article Open

Three Gravitational Lenses for the Price of One: Enhanced Strong Lensing through Galaxy Clustering

Abstract

We report the serendipitous discovery of two strong gravitational lens candidates (ACS J160919+6532 and ACS J160910+6532) in deep images obtained with the Advanced Camera for Surveys on the Hubble Space Telescope, each less than 40'' from the previously known gravitational lens system CLASS B1608+656. The redshifts of both lens galaxies have been measured with Keck and Gemini: one is a member of a small galaxy group at z ≈ 0.63 that also includes the lensing galaxy in the B1608+656 system, and the second is a member of a foreground group at z ≈ 0.43. By measuring the effective radii and surface brightnesses of the two lens galaxies, we infer their velocity dispersions based on the passively evolving fundamental plane (FP) relation. Elliptical isothermal lens mass models are able to explain their image configurations within the lens hypothesis, with a velocity dispersion compatible with that estimated from the FP for a reasonable source-redshift range. Based on the large number of massive early-type galaxies in the field and the number density of faint blue galaxies, the presence of two additional lens systems around CLASS B1608+656 is not unlikely in hindsight. Gravitational lens galaxies are predominantly early-type galaxies, which are clustered, and the lensed quasar host galaxies are also clustered. Therefore, obtaining deep high-resolution images of the fields around known strong-lens systems is an excellent method of enhancing the probability of finding additional strong gravitational lens systems.

Additional Information

© 2006 The American Astronomical Society. Received 2006 March 16; accepted 2006 July 9. Based in part on observations made with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555. These observations are associated with program GO-10158. These observations would not have been possible without the expertise and dedication of the staffs of the Palomar and Keck observatories. We especially thank Karl Dunscombe, Grant Hill, Jean Mueller, Gary Puniwai, Kevin Rykoski, Gabrelle Saurage, and Skip Staples. We thank the anonymous referee for timely comments that led to improvements to the paper. C. D. F. and J. P. M. acknowledge support under HST program GO-10158. Support for program GO-10158 was provided by NASA through a grant from the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555. This work is supported in part by the European Community's Sixth Framework Marie Curie Research Training Network Programme, contract MRTN-CT-2004-505183 ''ANGLES.'' Based in part on observations made with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555. These observations are associated with program GO-10158. 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. Based on observations obtained at the Gemini Observatory, which is operated by the Association of Universities for Research in Astronomy, Inc., under a cooperative agreement with the NSF on behalf of the Gemini partnership: the National Science Foundation (United States), the Particle Physics and Astronomy Research Council (United Kingdom), the National Research Council (Canada), CONICYT (Chile), the Australian Research Council (Australia), CNPq (Brazil), and CONICET (Argentina). Facilities: HST (ACS), Keck:I (LRIS), Keck:II (ESI), Gemini: Gillett (GMOS-North), PO:1.5m (CCD13).

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Published - Fassnacht_2006_ApJ_651_667.pdf

Submitted - 0603445.pdf

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Additional details

Created:
August 19, 2023
Modified:
October 20, 2023