The building blocks of 3D models of barred galaxies

We make an orbital study of a Milky Way-like model of a barred galaxy of three degrees of freedom, with a relatively small bar perturbation (12% in forces). We find the planar PL 1, 2 family of orbits, which is the continuation of the Lagrangian equilibrium points, L 1, 2 , for energy levels above E nL 1, 2 , and study its stability indices, b 1 , b 2 . Then with the help of the 4D Poincaré surfaces of section (PSSs) of the 6D phase space in several energy levels, we find 3D sticky chaotic orbits lying above (having a small third dimension) the planar PL 2 orbits, as well as above other planar unstable periodic orbits, outside corotation, that behave like regular ones and support ring structures of R 1 and R 1 R 2 type (on the plane of rotation) for a very long time compared to the Hubble time. We find that these sticky chaotic orbits quickly get diffused outside the system after tens or hundreds of Hubble times through a superdiffusing procedure that lasts for a certain time period, and that they will finally escape from the system through an Archimedean spiral converging to ballistic motion.