  The baryon acoustic oscillation (BAO) feature provides an important distance
scale for the measurement of the expansion history of the Universe. Theoretical
models of the BAO in the distribution of biased tracers of the large scale
structure usually rely on an initially linear BAO. With aid of N-body
simulations, we demonstrate that the BAO in the initial (Lagrangian) halo
2-point function is significantly sharper than in the linear matter
distribution, in agreement with peak theory. Using this approach, we delineate
the scale-dependence induced by the higher-derivative and velocity bias before
assessing how much of the initial BAO enhancement survives until the collapse
epoch. Finally, we discuss the extent to which the velocity or gravity bias,
which is also imprinted in the displacement field of halos, affects the
contrast of the BAO obtained with a reconstruction.

Cosmology and Nongalactic Astrophysics