Neutral hydrogen in the post-reionization universe
  The evolution of neutral hydrogen (HI) across redshifts is a powerful probe
of cosmology, large scale structure in the universe and the intergalactic
medium. Using a data-driven halo model to describe the distribution of HI in
the post-reionization universe ($z \sim $ 5 to 0), we obtain the best-fitting
parameters from a rich sample of observational data: low redshift 21-cm
emission line studies, intermediate redshift intensity mapping experiments, and
higher redshift Damped Lyman Alpha (DLA) observations. Our model describes the
abundance and clustering of neutral hydrogen across redshifts 0 - 5, and is
useful for investigating different aspects of galaxy evolution and for
comparison with hydrodynamical simulations. The framework can be applied for
forecasting future observations with neutral hydrogen, and extended to the case
of intensity mapping with molecular and other line transitions at intermediate
redshifts.
