Gravitational lenses and the structure of galaxies

Nearly singular isothermal mass distributions with small core radii are consistent with stellar dynamics, lens statistics, and lens models as a model for E/SO galaxies. Models like the de Vaucouleurs model with a constant mass-to-light ratio are not. While the isothermal distributions are probably an oversimplification, E/SO galaxies (at least in projection) must have significant amounts of dark matter on scales of an effective radius.