Spherical models for early-type galaxies with cuspy mass densities

Spherical mass density models are used to fit the central surface brightness profiles of early-type galaxies which are generated from Nuker law parameters obtained from the literature. The mass density and the corresponding potential are in an analytical form. It is shown that only a few mass density components are necessary to obtain a good fit and that for all power-law galaxies and for the core galaxies that we consider, most or all of the mass density components must have cusps to provide good fits. The applied quadratic programming fitting allows for a method of deprojection, which is reliable and convenient. The results can be used directly for further dynamical modelling.