Velocity profiles of Osipkov-Merritt models

Abstract

A simple algorithm is presented for the calculation of the projected line-of-sight velocity profiles (VPs) of non-rotating anisotropic spherical stellar dynamical models with a phase-space distribution function of the Osipkov-Merritt type. The velocity distribution in these models is isotropic inside the anisotropy radius r_a and becomes increasingly radially biased at larger radii. VP shape parameters are presented for a family of models in which the luminous mass density has an r^{-gamma} power-law cusp at small radii and an r^{-4} power-law fall-off at large radii. Self-consistent models and models in which the luminous matter is embedded in a dark halo are discussed. The effects of changes in the cusp slope gamma and in the anisotropy radius r_a are documented, and the area in the (gamma,r_a)-plane that contains physical models is delineated. The shapes of the VPs of the models show a considerable (and observable) variation with projected galactocentric radius. These models will be useful for interpreting the data on the VP shapes of elliptical galaxies that are now becoming available.

10 pages, uuencoded compressed PostScript, includes 7 figures

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