The Evolution of Gravitational Lens Galaxies

Most gravitational lens galaxies are early-type galaxies in relatively low density environments. We show that they lie on the same fundamental plane as early-type galaxies in both local and distant rich clusters. Their surface brightness evolution requires a typical star formation epoch of z=2-3, almost indistinguishable from that of rich cluster galaxies at comparable redshifts. The restricted galaxy type range of the lenses means that photometric redshifts work well even with only 1-3 filter photometry. We make preliminary measurements of the mass and luminosity functions of the lens galaxies, and find they are consistent with the standard model used for deriving cosmological limits using lens statistics. As expected for a mass-weighted sample, they are more massive and more luminous than the overall early-type galaxy population.