3D chaotic diffusion in barred spiral galaxies

Abstract

We study the diffusion of 3D orbits in an N-body model simulating a barred spiral galaxy. 3D chaotic orbits with initial conditions close to stable or unstable periodic orbits, inside corotation, stay trapped close to rotational tori or along unstable asymptotic manifolds, in the 4D phase space, and support the shape of the bar for very long times compared to the age of the Universe, before getting diffused outwards through ‘Arnold diffusion’ and finally escape from the system. During their initial time of diffusion, these orbits support the inner parts of the spiral structure of the galaxy. On the other hand 3D chaotic orbits with initial conditions outside corotation can stay close and along unstable asymptotic manifolds (in cases when no rotational tori exist at all), supporting the outer parts of the spiral structure of the galaxy for approximately 1/3 of the Hubble time.