CBL - Campus del Baix Llobregat

Projecte llegit

Títol: Efectos dinámicos de las galaxias con doble barra asimétrica sobre la estructura orbital

Estudiants que han llegit aquest projecte:

Director/a: SÁNCHEZ MARTÍN, PATRICIA

Departament: MAT

Títol: Efectos dinámicos de las galaxias con doble barra asimétrica sobre la estructura orbital

Data inici oferta: 28-01-2026     Data finalització oferta: 28-09-2026


Estudis d'assignació del projecte:
    GR ENG SIST AEROESP
Tipus: Individual
 
Lloc de realització: EETAC
 
Paraules clau:
Dynamical Systems, Differential Equations, Galaxies
 
Descripció del contingut i pla d'activitats:
Barred galaxies are characterized by a central stellar bar that influences galactic dynamics through the stability of the equilibrium points. A significant subset of these systems hosts double bars: a shorter inner and a longer outer bar oriented at different angles to one another. Modeling the galaxy with a 2D analytical potential, this project investigates how the mass ratio and length ratio between the two bars affect the location and stability of equilibrium points, and how asymmetric mass distributions within each bar further modify these dynamical properties. By analyzing these factors systematically, we aim to understand how structural parameters control the morphology of galactic spiral arms and the overall dynamical response of the galaxy.
 
Overview (resum en anglès):
The origin of spiral arms in barred galaxies and their relation to the internal structure of the system remains an open line of research in galactic dynamics. Several studies based on the dynamical systems approach, which models the galaxy through an analytical gravitational potential, have shown that the invariant manifolds emerging from periodic orbits around unstable equilibrium points determine the morphology of spiral arms. In this context, studying how these equilibrium points behave when asymmetries are introduced could help explain the existence of galaxies with atypical arm morphologies, such as galaxies with multiple spiral arms or with asymmetric arms. This work extends a single-bar barred galaxy model to a double-bar model, incorporating a secondary bar rotated with respect to the primary one, with the aim of studying the effect of asymmetries generated by bars with asymmetric mass distributions, or not centered on the galaxy's center of mass, on the orbital structure of the system. To this end, the numerical continuation tool COCO is used, which allows the evolution of the Lagrangian equilibrium points to be analyzed as the galactic model parameters are varied, and the associated bifurcations to be detected. From the configurations with three or more unstable equilibrium points, the galactic arms are simulated by means of particle integration and by computing the invariant manifolds. The results show that the rotation of the secondary bar with respect to the primary one, especially for angles close to 1.57 rad, favors the appearance of bifurcations and the coexistence of three or more unstable equilibrium points. Likewise, different modifications to the mass and geometry of the bars produce analogous effects on the configuration of these points. Finally, displacing a massive bulge, used to introduce an internal asymmetry in one of the bars, generates bifurcations similar to those obtained by displacing the halo, indicating that both types of asymmetry (external and internal) affect the orbital structure of the system in an equivalent way. Regarding the galactic arms obtained from these configurations, a case of particular interest is identified that could contain three galactic arms: the two lower arms, spiral-shaped, originate from the same end of the primary bar, while the upper arm has a very open ring-like shape. This work thus proposes a new scenario for the study of asymmetric double-barred galaxies and explores a range of configurations that could give rise to multiple spiral-arm morphologies.

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