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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/S0 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/S0 galaxies (at least in projection) must have significant amounts of dark matter on scales of an effective radius.