Runaway Stars, Hypervelocity Stars, and Radial Velocity Surveys
  Runaway stars ejected from the Galactic disk populate the halo of the Milky
Way. To predict the spatial and kinematic properties of runaways, we inject
stars into a Galactic potential, compute their trajectories through the Galaxy,
and derive simulated catalogs for comparison with observations. Runaways have a
flattened spatial distribution, with higher velocity stars at Galactic
latitudes less than 30 degrees. Due to their shorter stellar lifetimes, massive
runaway stars are more concentrated towards the disk than low mass runaways.
Bound (unbound) runaways that reach the halo probably originate from distances
of 6--12 kpc (10--15 kpc) from the Galactic center, close to the estimated
origin of the unbound runaway star HD 271791. Because runaways are brighter and
have smaller velocities than hypervelocity stars (HVSs), radial velocity
surveys are unlikely to confuse runaway stars with HVSs. We estimate that at
most 1 runaway star contaminates the current sample. We place an upper limit of
2% on the fraction of A-type main sequence stars ejected as runaways.
