Calibrating the Baryon Oscillation Ruler for Matter and Halos
  We characterize the nonlinear evolution of the baryon acoustic feature as
traced by the dark matter and halos, using a combination of perturbation theory
and N-body simulations. We confirm that the acoustic peak traced by the dark
matter is both broadened and shifted as structure forms, and that this shift is
well described by second-order perturbation theory. These shifts persist for
dark matter halos, and are a simple function of halo bias, with the shift
(mostly) increasing with increasing bias. Extending our perturbation theory
results to halos with simple two parameter bias models (both in Lagrangian and
Eulerian space) quantitatively explains the observed shifts. In particular, we
demonstrate that there are additional terms that contribute to the shift that
are absent for the matter. At z=0 for currently favored cosmologies, the matter
shows shifts of ~0.5%, b=1 halos shift the acoustic scale by ~0.2%, while b=2
halos shift it by ~0.5%; these shifts decrease by the square of the growth
factor at higher redshifts. These results are easily generalized to galaxies
within the halo model, where we show that simple galaxy models show marginally
larger shifts than the correspondingly biased halos, due to the contribution of
satellites in high mass halos. While our focus here is on real space, our
results make specific predictions for redshift space. For currently favored
cosmological models, we find that the shifts for halos at z=0 increase by
~0.3%; at high z, they increase by ~0.5% D^2. Our results demonstrate that
these theoretical systematics are smaller than the statistical precision of
upcoming surveys, even if one ignored the corrections discussed here. Simple
modeling, along the lines discussed here, has the potential to reduce these
systematics to below the levels of cosmic variance limited surveys.
