Characterization of Orbits in Bars in Disc Galaxies Using Fourier Frequencies
Abstract
Bars are among the most prominent dynamical structures in disc galaxies, yet their long-term evolution and the orbital families that sustain them remain only partially understood. In this work, we introduce a new methodology based on frozen potentials combined with Fourier analysis of particle trajectories to identify regular and sticky orbits in self-consistent N-body simulations. This approach allows us to isolate particles belonging to the x1 family, directly associated with the bar, and the x2 family, linked to a secondary perpendicular structure. Tracking these orbits across multiple snapshots enables us to quantify the time evolution of key bar properties, including its mass fraction, semi-axes, and density profile. Compared with established used diagnostics, our method provides the closest match to the temporal behaviour of the Fourier bar-strength parameter A2, while offering a direct dynamical interpretation and full three-dimensional characterization that Fourier-based approaches cannot provide. Our analysis further reveals that the indices nx, ny, and nz describing the bar density distribution are anisotropic and rarely equal to the canonical n=2 assumed in Ferrers profiles, highlighting the limitations of standard analytical approximations. We also find strong correlations between bar growth, orbital chaoticity, and angular momentum redistribution, with the bar acting both as a sink and as a driver of angular momentum transfer. A comparison between the two models analysed shows that rapidly forming bars are weaker and less stable than those that grow more gradually. Altogether, our methodology provides a robust framework for linking orbital structure to the dynamical evolution of barred galaxies.
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BibTeX
@misc{silvacastro2026characterization,
title = {{Characterization of Orbits in Bars in Disc Galaxies Using Fourier Frequencies}},
author = {A. Silva-Castro and I. Puerari and D. Valencia-Enríquez},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2609.09452},
eprint = {2609.09452},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2609.09452},
}
RIS
TY - UNPB
TI - Characterization of Orbits in Bars in Disc Galaxies Using Fourier Frequencies
AU - A. Silva-Castro
AU - I. Puerari
AU - D. Valencia-Enríquez
PY - 2026
DA - 2026/09/10
PB - arXiv
DO - 10.48550/arxiv.2609.09452
UR - https://arxiv.org/abs/2609.09452
AB - Bars are among the most prominent dynamical structures in disc galaxies, yet their long-term evolution and the orbital families that sustain them remain only partially understood. In this work, we introduce a new methodology based on frozen potentials combined with Fourier analysis of particle trajectories to identify regular and sticky orbits in self-consistent N-body simulations. This approach allows us to isolate particles belonging to the x_1 family, directly associated with the bar, and the x_2 family, linked to a secondary perpendicular structure. Tracking these orbits across multiple snapshots enables us to quantify the time evolution of key bar properties, including its mass fraction, semi-axes, and density profile. Compared with established used diagnostics, our method provides the closest match to the temporal behaviour of the Fourier bar-strength parameter A_2, while offering a direct dynamical interpretation and full three-dimensional characterization that Fourier-based approaches cannot provide. Our analysis further reveals that the indices n_x, n_y, and n_z describing the bar density distribution are anisotropic and rarely equal to the canonical n=2 assumed in Ferrers profiles, highlighting the limitations of standard analytical approximations. We also find strong correlations between bar growth, orbital chaoticity, and angular momentum redistribution, with the bar acting both as a sink and as a driver of angular momentum transfer. A comparison between the two models analysed shows that rapidly forming bars are weaker and less stable than those that grow more gradually. Altogether, our methodology provides a robust framework for linking orbital structure to the dynamical evolution of barred galaxies.
ER -