Triaxial orbit based galaxy models with an application to the (apparent) decoupled core galaxy NGC 4365

TL;DR

This paper introduces a flexible method for constructing triaxial galaxy models with black holes, fitting full velocity data, and applies it to NGC 4365 to analyze its internal structure and kinematic features.

Contribution

The paper presents a novel, general Schwarzschild-based approach for triaxial galaxy modeling that handles realistic luminosity profiles and full velocity distributions.

Findings

Successfully reproduces theoretical models

Recovers phase-space distribution function

Finds NGC 4365's core is not distinct from the main galaxy body

Abstract

We present a flexible and efficient method to construct triaxial dynamical models of galaxies with a central black hole, using Schwarzschild's orbital superposition approach. Our method is general and can deal with realistic luminosity distributions, which project to surface brightness distributions that may show position angle twists and ellipticity variations. The models are fit to measurements of the full line-of-sight velocity distribution (wherever available). We verify that our method is able to reproduce theoretical predictions of a three-integral triaxial Abel model. In a companion paper (van de Ven, de Zeeuw & van den Bosch), we demonstrate that the method recovers the phase-space distribution function. We apply our method to two-dimensional observations of the E3 galaxy NGC 4365, obtained with the integral-field spectrograph SAURON, and study its internal structure, showing that the observed kinematically decoupled core is not physically distinct from the main body and the inner region is close to oblate axisymmetric.