TESTING COSMOLOGICAL MODELS BY GRAVITATIONAL LENSING - I - METHOD ANDFIRST APPLICATIONS

Gravitational lensing directly measures mass density fluctuations alon g the lines of sight to very distant objects. No assumptions need to b e made concerning bias, the ratio of fluctuations in galaxy density to mass density. Hence, lensing is a very useful tool for studying the u niverse at low to moderate redshifts. We describe in detail a new meth od for tracing light rays from redshift zero through a three-dimension al mass distribution to high redshift. As an example, this method is a pplied here to a standard cold dark matter universe. We obtain a varie ty of results, some of them statistical in nature, others from rather detailed case studies of individual lines of sight. Among the statisti cal results are the frequency of multiply imaged quasars, the distribu tion of separation of multiple quasars, and the redshift distribution of lenses, all as functions of quasar redshift. We find effects rangin g from very weak lensing to highly magnified multiple images of high-r edshift objects, which for extended background sources (i.e., galaxies ) range from slight deformation of shape to tangentially aligned arcle ts to giant luminous arcs. Different cosmological models differ increa singly with redshift in their predictions of mass (and thus gravitatio nal potential) distributions. Our ultimate goal is to apply this metho d to a number of cosmogonic models and to eliminate some models for wh ich the gravitational lensing properties are inconsistent with those o bserved.