Modeling The Large Scale Bias of Neutral Hydrogen
  We present new analytical estimates of the large scale bias of neutral
hydrogen (HI). We use a simple, non-parametric model which monotonically
relates the total mass of a halo M_tot with its HI mass M_HI at zero redshift;
for earlier times we assume limiting models for the HI density evolution
consistent with the data presently available, as well as two main scenarios for
the evolution of our M_HI - M_tot relation. We find that both the linear and
the first nonlinear bias terms exhibit a strong evolution with redshift,
regardless of the specific limiting model assumed for the H I density over
time. These analytical predictions are then shown to be consistent with
measurements performed on the Millennium Simulation. Additionally, we show that
this strong bias evolution does not sensibly affect the measurement of the HI
power spectrum.
