Completely analytical families of anisotropic gamma-models

Abstract

We present new analytical distribution functions for anisotropic spherical galaxies. They have the density profiles of the gamma-models, which allow a wide range of central density slopes, and are widely used to fit elliptical galaxies and the bulges of spiral galaxies. Most of our models belong to two two-parameter families. One of these parameters is the slope gamma of the central density cusp. The other allows a wide range of varying radial and tangential anisotropies, at either small or large radii. We give analytical formulas for their distribution functions, velocity dispersions, and the manner in which energy and transverse velocity are distributed between orbits. We also give some of their observable properties, including line-of-sight velocity profiles which have been computed numerically. Our models can be used to provide a useful tool for creating initial conditions for N-body and Monte Carlo simulations.

arXiv comment21 pages, 15 figures, accepted for publication in MNRAS

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• Two-component galaxy models: the effect of density profile at large radii on the phase-space consistency
• The double-power approach to spherically symmetric astrophysical systems
• Analytical galactic models with mild stellar cusps
• Distribution Function of Dark Matter with Constant Anisotropy