México
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A study of stellar orbits in a logarithmic non axisymmetric rotating potential
Autor
LUIS LEONARDO CHAVES VELASQUEZ
Resumen
In this thesis a study of the theoretical foundations of stellar orbits in non axisymmetric
rotating potentials has been made. Before to get into the study of
orbits integrated numerically, the linear theory was studied. In this approximation
the non-axisymmetry of a potential is taken as a first order perturbation.
Using this approximation, the called characteristic curves were built analytically
using an isochrone potential. In that way, it was understood how orbits that
have been integrated in an inertial frame, closes in a rotating frame to form a
characteristic curve.
Specifically the GALI2 index and the shooting method were applied in order
to build the characteristic curves numerically. These characteristic curves were
constructed for a logarithmic potential keeping the pattern speed equal to the
unity and varying the axial ratio with values q = 1, q = 0.8, and q = 0.4. The
system of differential equations were integrated numerically for 10 Gyrs and our
integrator keeps the error in the energy below 10−12 order.
In the axisymmetric case (q = 1) all the families of orbits are stable, therefore
they keep their morphology for 10 Gyr. In the non-axisymmetric cases it is
found that the non-axisymmetry induces chaos on the characteristic curve and
some families disappear. The X1 family is found at q = 0.8 and q = 0.4. In both
cases this family is stable at lower energies, but some of its members are unstable
at higher energies. The stable members of the X1 family are the backbones of
the bar structure.
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