Galaxy Models with Tangentially Anisotropic Velocity Distributions

This paper provides two families of flexible and simple galaxy models.Representatives of many of the families possess the important cosmologicalcusps, with the density behaving like 1/r or 1/r^1.33 or 1/r^1.5 at smallradii. The density falls off between 1/r^3 and 1/r^5 at large radii. We provideanalytic and anisotropic distribution functions for all the models. Unlike manyexisting methods, our algorithm can yield tangentially anisotropic velocitydispersions in the outer parts, and so is useful for modeling populations ofsatellite galaxies and substructure in host galaxy halos. As an application, wedemonstrate the degeneracy between mass and anisotropy for the satellite galaxypopulation of the Milky Way. This can introduce a factor of ~3 uncertainty inthe mass of the Milky Way as inferred from the kinematics of the satellitepopulation.Comment: to appear in AJ, extended appendix, typo corrected from the 2nd version (completely rewritten from the 1st version, see also astro-ph/0508419 for some materials split from the 1st version