A Survey for LargeImage Separation Lensed Quasars

摘要

The statistics of gravitationally lensed quasars with multiple images in the 0".17" range have been measured in various surveys. Little is known, however, about lensed-quasar statistics at larger image separations, which probe masses on the scale of galaxy clusters. We extend the results of the Hubble Space Telescope (HST) Snapshot Survey for Lensed Quasars to the 7"50" range for a subsample of 76 quasars that is free of known selection effects. Using a combination of multicolor photometry and spec- troscopy, we show that none of the point sources in the entire field of view of the HST observations of these quasars are lensed images. Large-separation quasar lensing is therefore not common. We carry out a detailed calculation of the expected statistics of large-separation lensing for this quasar sample, incorp- orating realistic input for the mass profiles and mass function of galaxy clusters.