Determining the lensing fraction of SDSS quasars: Methods and results from the early data release

Abstract

We present an algorithm for selecting gravitational lens candidates from among Sloan Digital Sky Survey (SDSS) quasars. In median Early Data Release (EDR) conditions, the algorithm allows for the recovery of pairs of equal flux point sources down to separations of ∼0″.7 or with flux ratios up to ∼10:1 at a separation of 1″.5. The algorithm also recovers a wide variety of plausible quad geometries. We also present a method for determining the selection function of this algorithm through the use of simulated SDSS images and introduce a method for calibrating our simulated images through truth testing with real SDSS data. Finally, we apply our algorithm and selection function to SDSS quasars fr..