Warp evidences in precessing galactic bar models
  Most galaxies have a warped shape when they are seen from an edge-on point of
view. The reason for this curious form is not completely known so far and in
this work we apply dynamical system tools to contribute to its explanation.
Starting from a simple, but realistic, model formed by a bar and a disc, we
study the effect produced by a small misalignment between the angular momentum
of the system and its angular velocity. To this end, a precession model is
developed and considered, assuming that the bar behaves like a rigid body.
After checking that the periodic orbits inside the bar keep being the skeleton
of the inner system, even after inflicting a precession to the potential, we
compute the invariant manifolds of the unstable periodic orbits departing from
the equilibrium points at the ends of the bar to get evidences of their warped
shapes. As it is well known, the invariant manifolds associated with these
periodic orbits drive the arms and rings of barred galaxies and constitute the
skeleton of these building blocks. Looking at them from a side-on viewpoint, we
find that these manifolds present warped shapes as those recognized in
observations. Lastly, test particle simulations have been performed to
determine how the stars are affected by the applied precession, confirming this
way the theoretical results obtained.
