Heated Disc Stars in the Stellar Halo
  Minor accretion events with mass ratio M_sat : M_host ~ 1:10 are common in
the context of LCDM cosmology. We use high-resolution simulations of
Galaxy-analogue systems to show that these mergers can dynamically eject disk
stars into a diffuse light component that resembles a stellar halo both
spatially and kinematically. For a variety of orbital configurations, we find
that ~3-5e8 M_sun of primary stellar disk material is ejected to a distance
larger than 5 kpc above the galactic plane. This ejected contribution is
similar to the mass contributed by the tidal disruption of the satellite galaxy
itself, though it is less extended. If we restrict our analysis to the
approximate solar neighborhood in the disk plane, we find that ~1% of the
initial disk stars in that region would be classified kinematically as halo
stars. Our results suggest that the inner parts of galactic stellar halos
contain ancient disk stars and that these stars may have been liberated in the
very same events that delivered material to the outer stellar halo.
