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Projecte llegit

Títol: Òrbites periòdiques en glàxies barrades no centrades

Estudiants que han llegit aquest projecte:

Director/a: SÁNCHEZ MARTÍN, PATRICIA

Departament: MAT

Títol: Òrbites periòdiques en glàxies barrades no centrades

Data inici oferta: 27-12-2023     Data finalització oferta: 27-07-2024


Estudis d'assignació del projecte:
    DG ENG AERO/SIS TEL
    DG ENG AERO/TELEMÀT
Tipus: Individual
 
Lloc de realització: EETAC
 
Segon director/a (UPC): MASDEMONT SOLER, JOSEP JOAQUIM
 
Paraules clau:
Dynamical Systems, Differential Equations, Galaxies
 
Descripció del contingut i pla d'activitats:
Barred galaxies, distinguished by the presence of a central bar composed of stars, exhibit a notable dynamical behavior wherein periodic orbits within the bar contribute to the structural integrity of the bar itself. However, in some galaxies, such as the Large Magellanic Cloud, the bar is displaced from its central position, which prompts an inquiry into the longevity of the structural stability of the bar under such conditions. This investigation is based on a detailed analysis of periodic orbits within novel configurations where the bar is non-centered. By studying these configurations, we aim to ascertain whether the displacement from the galactic center has a discernible impact on its long-term stability. The outcomes of this study are intended to deepen our understanding of the intricate dynamical interaction within barred galaxies.
 
Overview (resum en anglès):
In the universe, there are various types of galaxies, some of which feature a bar with a high density of stars. Previous studies have demonstrated that, when the different elements of the galactic system (bar, bulge, disk, and halo) are arranged symmetrically with respect to a rotating coordinate system aligned with the bar, the periodic orbits that form around the central equilibrium point are responsible for shaping the bar. This phenomenon allows the bar to persist over time. Additionally, when studying galactic dynamics, the entire bar can be considered as a rigid body. All of this has been demonstrated for a symmetric arrangement, but many galaxies do not follow this model. Therefore, this project studies the periodic orbits around the central equilibrium point of the galactic system in cases where some form of asymmetry is present. This provides a preliminary understanding of the behavior in these cases, which can then be compared with the previously studied symmetric case.

To carry out this study, a dynamic system model is studied that allows to describe the system's elements and determine its dynamics. Different density distributions and potentials, proposed by various models previously used in the study of the symmetric case, are employed. Using these, the vector field of the galactic system can be defined, allowing to calculate the equilibrium point distribution, which varies depending on the introduced asymmetries. Then, by identifying the central equilibrium point for each asymmetric case, the calculation of periodic orbits can be developed, first in its vicinity and then, using a continuation method, more periodic orbits of the same family can be found.

From the calculations, for a distribution where the galaxy's bar is vertically displaced from the reference system's center, but the bulge remains at the center of the bar, an asymmetric result is observed in terms of the equilibrium points, although the orbits have the same shape as in the symmetric case. Therefore, in this scenario, the periodic orbits continue shaping the bar in the same way. However, if the element causing the asymmetry is the bulge, displaced horizontally along the bar, the results show not only asymmetry in the equilibrium points, but also orbits with different shapes, which would cause the motion of stars inside to differ, potentially leading to concentrations of stars in certain regions of the bar. Finally, both displacements (bulge and bar) are combined, and the results show that the displacement of the equilibrium points is influenced by both asymmetries, but in terms of orbit shape, the bulge displacement has the greatest influence.

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