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M.D. Gregg, R.H. Becker (U.C. Davis and IGPP/LLNL), P.L. Schechter (M.I.T.), R.L. White (STScI), L. Wisotzki (U. Potsdam)
Most theories of quasar lensing predict more close separation lenses than are presently known. Deciding whether this deficit is real or an observational selection effect is important for using lenses to constrain the intervening galaxy mass distribution or cosmological models. We are conducting two imaging surveys of bright quasars to search for new examples of gravitational lensing, particularly those with small image separations. After about 200 snapshots during Cycles 8 and 9, the program using the imaging capability of the Space Telescope Imaging Spectrograph (STIS) has found three certain lensed quasars, with separations of 0.64" (Gregg et al. 2000), 1.2", and a surprisingly large 3.4". There are several additional promising candidates. The other survey is being conducted with the Near InfraRed Camera (NIRC) at Keck Observatory. While the NIRC effort has not yet turned up any confirmed lensed quasars, the K-band imaging has detected the lensing galaxy in two of the new STIS systems. We will present our results and analysis to date, including additional ground based follow-up imaging and spectroscopy of the lensed and candidate systems.
Support for this work is provided by NASA grants GO-8202 and GO-8631 from STScI, operated by AURA, Inc., under NASA contract NAS5-26555. This work was performed under the auspices of the U.S. Department of Energy by University of California Lawrence Livermore National Laboratory under contract No. W-7405-Eng-48.
Gregg, M.D., Wisotzki, L., Becker, R.H., Maza, J., Schechter, P. White, R.L., Brotherton, M.S., & Winn, J.N. 2000, AJ, 119, 2535.