Limits on the Number of Close Optical Quasar Pairs

Creators: Weedman, D. W.; Djorgovski, S.

Others:: Osmer, Patrick Stewart; Phillips, M. M.

Abstract

A new search has been conducted for close pairs of quasars with identical spectra, including both emission line objects and blue stellar objects. Survey plates covering 3.9 deg^2 were selected for image quality, full image widths being 0."8 to l."2. Although 200 to 400 quasar spectral images should have been examined, no candidate pairs with separations < 4" were found. Eight such pairs from 4" to 10" were found, but none were subsequently confirmed as lensed quasars. The selection bias is derived and applied to these limits. It is concluded that the absence of close pairs expected from gravitational lensing models cannot be explained by observational selection effects.

Additional Information

© 1988 Astronomical Society of the Pacific. Provided by the NASA Astrophysics Data System. DWW was a visiting astronomer on the Canada-France-Hawaii Telescope, operated by the National Research Council of Canada, the Centre National de la Recherche Scientifique of France, and the University of Hawaii. We thank the Canadian Allocation Committee for observing time on the CFHT and Rene' Racine for obtaining two of the plates used. SD thanks both Hyron Spinrad and the technical staff for their help in making it possible to obtain observations at the Lick Observatory, University of California. Also, William Keel is thanked for obtaining and processing the CCD image used for magnitude calibration. This research was partially supported by NSF grant AST-8101204.

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Published - 1988ASPC____2__226W.pdf

Published - 2-0226.pdf

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