Cusped Mass Models Of Gravitational Lenses

Recent observations of galaxy luminosity profiles and dark matter simulations find luminosity and mass distributions characterized by central cusps rather than finite core radii. We introduce and implement a set of cusped ellipsoidal lens models which include limits similar to the Jaffe, Hernquist, \eta and NFW models and apply them to the gravitational lenses APM 08279+5255 and B 1933+503. A successful model of APM 08279+5255 with its central, odd image requires a very shallow cusp, $\gamma \ltorder 0.4$ where $\rho \propto r^{-\gamma}$ as $r\to 0$, which is similar to a core rather than the favored $1 \ltorder \gamma \ltorder 2$ cusps. B~1933+503, by contrast, is well modeled with a steep density cusp, $1.6 \ltorder \gamma \ltorder 2.0$.