M/L and velocity anisotropy from observations of spherical galaxies, or must M87 have a massive black hole?

Abstract

An algorithm is developed that determines whether a given set of photometric and spectroscopic observations of a spherical galaxy are consistent with the mass-to-light ratio in the galaxy being constant. If such a model is possible, the value of the mass-to-light ratio and the values of the two independent components of velocity dispersion at each radius are determined. Tests of the algorithm demonstrate its consistency and accuracy when applied to pseudo-data generated from a variety of theoretical models. When the data do not extend to very great radii and must be extrapolated arbitrarily, qualitatively correct results are obtained.