Geneva University seminars

Neutral hydrogen in the post-reionization universe

by Hamsa Padhmanabhan (ETHZ)

Room 234 (Geneva University)

Room 234

Geneva University

24 quai E. Ansermet CH-1211 Genève 4
Mapping of the neutral hydrogen (HI) 21-cm intensity fluctuations across redshifts promises a novel and powerful probe of cosmology. The neutral hydrogen gas mass density, $\Omega_{\rm HI}$ and bias parameter, $b_{\rm HI}$ are key astrophysical inputs to the HI intensity fluctuation power spectrum. Astrophysical constraints on these two quantities come from a number of sources: galaxy surveys, HI intensity mapping experiments, Damped Lyman-Alpha (DLA) system observations, theoretical prescriptions for assigning HI to dark matter halos, and the results of numerical simulations. I will describe how the combination of the current constraints leads to bounds on the HI power spectrum over redshifts 0-3.5. In the literature, there exist different analytical prescriptions for modelling the 21-cm (emission line surveys/intensity mapping experiments) and Damped Lyman-Alpha (DLA) observations of the post-reionization HI. I will describe the reconciliation of these two differing approaches towards a consistent model of the distribution and evolution of HI across z ~ 0 - 4. The model has implications for the characteristic host halo masses of the DLAs and the power spectrum of 21-cm intensity fluctuations.
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