On the identification of merger debris in the {\it Gaia} Era
  We model the formation of the Galactic stellar halo via the accretion of
satellite galaxies onto a time-dependent semi-cosmological galactic potential.
Our goal is to characterize the substructure left by these accretion events in
a close manner to what may be possible with the {\it Gaia} mission. We have
created a synthetic {\it Gaia} Solar Neighbourhood catalogue by convolving the
6D phase-space coordinates of stellar particles from our disrupted satellites
with the latest estimates of the {\it Gaia} measurement errors, and included
realistic background contamination due to the Galactic disc(s) and bulge. We
find that, even after accounting for the expected observational errors, the
resulting phase-space is full of substructure. We are able to successfully
isolate roughly 50% of the different satellites contributing to the `Solar
Neighbourhood' by applying the Mean-Shift clustering algorithm in
energy-angular momentum space. Furthermore, a Fourier analysis of the space of
orbital frequencies allows us to obtain accurate estimates of time since
accretion for approximately 30% of the recovered satellites.
