Constraints on Cosmology and Galaxy Evolution Using Gravitational Lensing

Pedro R. Capelo, Priyamvada Natarajan

The redshift distribution of galaxy lenses in known gravitational lens systems provides a powerful test that can potentially discriminate amongst cosmological and galaxy evolution models. The image shows the lens system Q0142-100, with the lens-galaxy at the centre and two lensed images of a distant quasar. From measuring the lens-image separation and the quasar redshift, we can calculate the lens-redshift probability for such a system, using Einstein's theory of general relativity. By comparing it to the actual galaxy redshift, we can derive the most probable cosmological model. We apply the lens-redshift test to a large sample of verified lens systems derived from recent observations in large surveys, primarily from the Sloan Digital Sky Survey and the Cosmic Lens All Sky Survey, and investigate the effects on robust retrieval of the value of the classical cosmological constant.