Testing Cosmological Models by Gravitational Lensing. I. Method and First Applications

Gravitational lensing directly measures mass density fluctuations along thelines of sight to very distant objects. No assumptions need to be madeconcerning bias, the ratio of fluctuations in galaxy density to mass density.Hence, lensing is a very useful tool to study the universe at low to moderateredshifts. We describe in detail a new method to trace light rays from redshift zerothrough a three dimensional mass distribution to high redshift. As an example,this method is applied here to a standard cold dark matter universe. We obtaina variety of results, some of them statistical in nature, others from ratherdetailed case studies of individual ``lines of sight". Among the former are thefrequency of multiply imaged quasars, the distribution of separation of themultiple quasars, and the redshift distribution of lenses: all that as afunction of quasar redshift. We find effects from very weak lensing to highlymagnified multiple images of high redshift objects, which, for extendedbackground sources, (i.e. galaxies), range from slight deformations of theshapes through tangentially aligned arclets up to giant luminous arcs. Different cosmological models differ, increasingly with redshift, in theirpredictions for the mass (thus gravitational potential) distributions. Ourultimate goal is to apply this method to a number of cosmogonic models and toeliminate some models whose gravitational lensing properties are inconsistentwith those observed.