A family of lowered isothermal models

TL;DR

This paper introduces a versatile family of spherical, lowered isothermal models with adjustable anisotropy and energy truncation, suitable for describing star clusters at various evolutionary stages.

Contribution

It extends existing isotropic models by incorporating anisotropy and energy truncation, providing analytic expressions and a computational tool for data fitting and simulation.

Findings

Models accurately describe star cluster phase-space densities.

Analytic solutions facilitate efficient data analysis.

The Python implementation enables practical application.

Abstract

We present a family of self-consistent, spherical, lowered isothermal models, consisting of one or more mass components, with parameterised prescriptions for the energy truncation and for the amount of radially biased pressure anisotropy. The models are particularly suited to describe the phase-space density of stars in tidally limited, mass-segregated star clusters in all stages of their life-cycle. The models extend a family of isotropic, single-mass models by Gomez-Leyton and Velazquez, of which the well-known Woolley, King and Wilson (in the non-rotating and isotropic limit) models are members. We derive analytic expressions for the density and velocity dispersion components in terms of potential and radius, and introduce a fast model solver in PYTHON (LIMEPY), that can be used for data fitting or for generating discrete samples.