Excitation of coupled stellar motions in the Galactic Disk by orbiting
  satellites
  We use a set of high-resolution N-body simulations of the Galactic disk to
study its interactions with the population of satellites predicted
cosmologically. One simulation illustrates that multiple passages of massive
satellites with different velocities through the disk generate a wobble, having
the appearance of rings in face-on projections of the stellar disk. They also
produce flares in the disk outer parts and gradually heat the disk through
bending waves. A different numerical experiment shows that an individual
satellite as massive as the Sagittarius dwarf galaxy passing through the disk
will drive coupled horizontal and vertical oscillations of stars in underdense
regions, with small significant associated heating. This experiment shows that
vertical excursions of stars in these low-density regions can exceed 1 kpc in
the Solar neighborhood, resembling the coherent vertical oscillations recently
detected locally. They can also induce non-zero vertical streaming motions as
large as 10-20 km s$^{-1}$, consistent with recent observations in the Galactic
disk. This phenomenon appears as a local ring, with modest associated disk
heating.
