Self-consistent dynamical models with a finite extent -- III. Truncated power-law spheres

Abstract

Fully analytical dynamical models usually have an infinite extent, while real star clusters, galaxies, and dark matter haloes have a finite extent. The standard method for generating dynamical models with a finite extent consists of taking a model with an infinite extent and applying a truncation in binding energy. This method, however, cannot be used to generate models with a pre-set analytical mass density profile. We investigate the self-consistency and dynamical properties of a family of power-law spheres with a general tangential Cuddeford (TC) orbital structure. By varying the density power-law slope $\gamma$ and the central anisotropy ${\beta }_0$, these models cover a wide parameter space in density and anisotropy profiles. We explicitly calculate the phase-space distribution function for various parameter combinations, and interpret our results in terms of the energy distribution of bound orbits. We find that truncated power-law spheres can be supported by a TC orbital structure if and only if $\gamma ⩾2{\beta }_0$, which means that the central density slope-anisotropy inequality is both a sufficient and a necessary condition for this family. We provide closed expressions for structural and dynamical properties such as the radial and tangential velocity dispersion profiles, which can be compared against more complex numerical modelling results. This work significantly adds to the available suite of self-consistent dynamical models with a finite extent and an analytical description.

12 pages, 4 figures, accepted for publication in MNRAS

References in corpus (16)

• Statistical mechanics of collisionless orbits. I. Origin of central cusps in dark-matter halos
• Dynamical models with a general anisotropy profile
• The phase-space structure of tidally stripped halos
• Two-component galaxies with flat rotation curve
• The Einasto model for dark matter haloes
• Mapping the stability of stellar rotating spheres via linear response theory
• Two-component galaxy models: the effect of density profile at large radii on the phase-space consistency
• The differential energy distribution and the total integrated binding energy of dynamical models
• Truncated $\gamma$-exponential models for tidal stellar systems
• Constraints on velocity anisotropy of spherical systems with separable augmented densities
• On the augmented density of a spherical anisotropic dynamic system
• Multilayer spherical stellar cluster with uniform density
• The Effective Cross-sections of a Lensing-galaxy: Singular Isothermal Sphere with External Shear
• Self-consistent dynamical models with a finite extent -- II. Radially truncated models
• Investigating Dynamical Properties of Globular Clusters through a Family of Lowered Isothermal Models
• On radial anisotropy limits in stellar systems