Exploring the origin of moving groups and diagonal ridges by simulations
  of stellar orbits and birthplaces
  The present paper is the culminating one of a series aimed to contribute to
the understanding of the kinematic structures of the solar neighbourhood (SN),
explaining the origin of the Local Arm and relating the moving groups with the
spiral-arms resonances in the disk. With a model for the Galactic potential,
with the Sun inside the spiral corotation resonance (CR), we integrate the 2D
orbits of test particles distributed in birthplaces along the main spiral arms,
the Local Arm, and in the axisymmetric disk. A comparison of the resulting U-V
plane of the SN with that provided by Gaia DR2 confirms our previous conclusion
that the moving groups of Coma Berenices, Pleiades, and Hyades are associated
with the CR, and that the Hercules stream is formed by the bulk of high-order
inner Lindblad resonances. The kinematic structures result from stellar orbits
trapped by the spiral resonances in a timespan of ~ 1 Gyr, indicating the
long-living nature of the spiral structure and challenging recent arguments in
favor of short-lived structures originated from incomplete phase mixing in the
Galactic disk. As a byproduct, our simulations give some insight into the
birthplaces of the stars presently located in the SN; the majority of stars of
the main moving groups and the Hercules stream were likely born in the Local
Arm, while stars of the Sirius group possibly originated from the outer segment
of the Sagittarius-Carina arm. We also propose the spiral resonances as the
dynamical origin for the diagonal ridges in the Galactic distribution of
rotation velocities.
