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 an analytical, data-driven halo model to describe the distribution of HI in the post-reionization universe (z ~ 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 a useful tool for investigating different aspects of galaxy evolution as well as in the current and future intensity mapping experiments. I will discuss (i) forecasting future observations with neutral hydrogen and (ii) extensions to the model for the case of carbon monoxide intensity mapping at moderate redshifts.