Recovery of the internal orbital structure of galaxies

TL;DR

This paper introduces Abel models for galaxy dynamics, demonstrating their efficiency in capturing internal structures and applying Schwarzschild's method to recover galaxy properties from simulated observations.

Contribution

The paper develops and applies Abel models for axisymmetric and triaxial galaxies, enabling efficient calculation of dynamics and validation with Schwarzschild's orbit-superposition method.

Findings

Schwarzschild's method accurately recovers internal galaxy dynamics.

Abel models effectively simulate observed kinematic data.

Models capture complex internal structures of early-type galaxies.

Abstract

We construct axisymmetric and triaxial galaxy models with a phase-space distribution function that depends on linear combinations of the three exact integrals of motion for a separable potential. These Abel models, first introduced by Dejonghe & Laurent and subsequently extended by Mathieu & Dejonghe, are the axisymmetric and triaxial generalisations of the well-known spherical Osipkov-Merritt models. We show that the density and higher order velocity moments, as well as the line-of-sight velocity distribution (LOSVD) of these models can be calculated efficiently and that they capture much of the rich internal dynamics of early-type galaxies. We build a triaxial and oblate axisymmetric galaxy model with projected kinematics that mimic the two-dimensional kinematic observations that are obtained with integral-field spectrographs such as SAURON. We fit the simulated observations with axisymmetric and triaxial dynamical models constructed with our numerical implementation of Schwarzschild's orbit-superposition method. We find that Schwarzschild's method is able to recover the internal dynamics and three-integral distribution function of realistic models of early-type galaxies.