No memory of past warps in the vertical density structure of galaxies
  Warps are observed in a large fraction of disc galaxies, and can be due to a
large number of different processes. Some of these processes might also cause
vertical heating and flaring. Using a sample of galaxies simulated in their
cosmological context, we study the connection between warping and disc heating.
We analyse the vertical stellar density structure within warped stellar discs,
and monitor the evolution of the scale-heights of the mono-age populations and
the geometrical thin and thick disc during the warp's lifetime. We also compare
the overall thickness and the vertical velocity dispersion in the disc before
and after the warp. We find that for warps made of pre-existing stellar
particles shifted off-plane, the scale-heights do not change within the disc's
warped region: discs tilt rigidly. For warps made of off-plane new stellar
material (either born in-situ or accreted), the warped region of the disc is
not well described by a double $\mathrm{sech^2}$ density profile. Yet, once the
warp is gone, the thin and thick disc structure is recovered, with their
scale-heights following the same trends as in the region that was never warped.
Finally, we find that the overall thickness and vertical velocity dispersion do
not increase during a warp, regardless of the warp's origin. This holds even
for warps triggered by interactions with satellites, which cause disc heating
but before the warp forms. Our findings suggest that the vertical structure of
galaxies does not hold any memory of past warps.
