Angular separations of lensed quasar images

We have analyzed the observed image separations of the gravitationally lens ed images of quasars (QSOs) for a possible correlation with the source reds hift. Contrary to the previously noted anti-correlation based on a smaller data set, no correlation is found for the currently available data. We have calculated the average image separations of the lensed QSOs as a function of source redshifts for isothermal spheres with cores in a flat universe, t aking into account the amplification bias caused by lensing. The shape of t he distribution of the average image separation as a function of redshift i s very robust and is insensitive to most model parameters. Observations are found to be roughly consistent with the theoretical results for models tha t assume the lens distribution to be (1) a Schechter luminosity function th at, however, cannot produce images with large separation and (2) mass conde nsations in a cold dark matter universe, as given by the Press-Schechter th eory if an upper limit of 1 x 10(13)-7 x 10(13) M. is assumed on the mass o f the condensations.