Vertical density waves in the Milky Way disc induced by the Sagittarius
  Dwarf Galaxy
  Recently, Widrow and collaborators announced the discovery of vertical
density waves in the Milky Way disk. Here we investigate a scenario where these
waves were induced by the Sagittarius dwarf galaxy as it plunged through the
Galaxy. Using numerical simulations, we find that the Sagittarius impact
produces North-South asymmetries and vertical wave-like behavior that
qualitatively agrees with what is observed. The extent to which vertical modes
can radially penetrate into the disc, as well as their amplitudes, depend on
the mass of the perturbing satellite. We show that the mean height of the disc
is expected to vary more rapidly in the radial than in the azimuthal direction.
If the observed vertical density asymmetry is indeed caused by vertical
oscillations, we predict radial and azimuthal variations of the mean vertical
velocity, correlating with the spatial structure. These variations can have
amplitudes as large as 8 km/s.
