Lens galaxy properties of SBS 1520+530 : insights from Keck spectroscopy and AO imaging

Creators: Auger, M. W.; Fassnacht, C. D.; Wong, K. C.; Thompson, D.; Matthews, K.; Soifer, B. T.

Abstract

We report on an investigation of the SBS 1520+530 gravitational lens system. We have used archival Hubble Space Telescope (HST) imaging, Keck spectroscopic data, and Keck adaptive optics (AO) imaging to study the lensing galaxy and its environment. The AO imaging has allowed us to fix the lens galaxy properties with a high degree of accuracy when performing the lens modeling, and the data indicate that the lens has an elliptical morphology and perhaps a disk. The new spectroscopic data suggest that previous determinations of the lens redshift may be incorrect, and we report an updated, although inconclusive, value z(lens) = 0.761. We have also spectroscopically confirmed the existence of several galaxy groups at approximately the redshift of the lens system. We create new models of the lens system that explicitly account for the environment of the lens, and we also include improved constraints on the lensing galaxy from our AO imaging. Lens models created with these new data can be well fit with a steeper than isothermal mass slope (α = 2.29, where ρ propto r−α) if H_0 is fixed at 72 km s^(-1) Mpc^(-1); isothermal models require H_0 similar to 50 km s^(-1) Mpc^(-1). The steepened profile may indicate that the lens is in a transient perturbed state caused by interactions with a nearby galaxy.

Additional Information

© 2008. The American Astronomical Society. Received 2007 June 27; accepted 2007 October 9. We thank LoriLubin,DavidRusin, and JohnMcKean for useful discussions and helpful comments.We also thank the referee for helpful suggestions. This work is based in part on observations made with the National Aeronautics and Space Administration (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. 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 NASA. 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 has made use of the Sloan Digital Sky Survey (SDSS) database. Funding for the SDSS and SDSS-II has been provided by the Alfred P. Sloan Foundation, the Participating Institutions, the National Science Foundation, the US Department of Energy, NASA, the Japanese Monbukagakusho, the Max Planck Society, and the Higher Education Funding Council for England. Part of this work was supported by the European Community's Sixth Framework Marie Curie Research Training Network Programme, contract MRTN-CT-2004-505183 ''ANGLES.''

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