How does the Structure of Spherical Dark Matter Halos Affect the Types of Orbits in Disk Galaxies?
Abstract
The main objective of this work is to determine the character of orbits of stars moving in the meridional (R,z) plane of an axially symmetric time-independent disk galaxy model with a central massive nucleus and an additional spherical dark matter halo component. In particular, we try to reveal the influence of the scale length of the dark matter halo on the different families of orbits of stars, by monitoring how the percentage of chaotic orbits, as well as the percentages of orbits of the main regular resonant families evolve when this parameter varies. The smaller alignment index (SALI) was computed by numerically integrating the equations of motion as well as the variational equations to extensive samples of orbits in order to distinguish safely bet ween ordered and chaotic motion. In addition, a method based on the concept of spectral dynamics that utilizes the Fourier transform of the time series of each coordinate is used to identify the various families of regular orbits and also to recognize the secondary resonances that bifurcate from them. Our numerical computations reveal that when the dark matter halo is highly concentrated, that is when the scale length has low values the vast majority of star orbits move in regular orbits, while on the oth er hand in less concentrated dark matter halos the percentage of chaos increases significantly. We also compared our results with early related work.
- Publication:
-
Baltic Astronomy
- Pub Date:
- 2014
- DOI:
- 10.1515/astro-2017-0171
- arXiv:
- arXiv:1406.0446
- Bibcode:
- 2014BaltA..23...37Z
- Keywords:
-
- galaxies: kinematics and dynamics;
- galaxies: structure;
- chaos;
- dark matter;
- Astrophysics - Astrophysics of Galaxies
- E-Print:
- Published in Baltic Astronomy journal. arXiv admin note: previous papers with related context: arXiv:1404.4194, arXiv:1404.3961, arXiv:1309.5607