An Analytical Model for the Distribution of Image Separations in Gravitational Lensing

Using an analytical model, we compute the distribution of image separations resulting from gravitational lensing of distant sources, for 3 COBE-normalized CDM models. The model assumes that multiple imaging results only from lensing by individual galaxies, which are modelled as nonsingular isothermal spheres. The contribution of the background matter to the lensing is neglected. We found that, while the number of multiple-imaged sources can put strong constraints on the cosmological parameters, the distribution of image separations does not constrain the cosmological models in any significant way.