The atomic hydrogen content of the post-reionization Universe
Abstract
We present a comprehensive analysis of atomic hydrogen (H I) properties using a semi-analytical model of galaxy formation and N-body simulations covering a large cosmological volume at high resolution. We examine the H I mass function and the H I density, characterizing both their redshift evolution and their dependence on hosting halo mass. We analyse the H I content of dark matter haloes in the local Universe and up to redshift z = 5, discussing the contribution of different galaxy properties. We find that different assembly history plays a crucial role in the scatter of this relation. We propose new fitting functions useful for constructing mock H I maps with halo occupation distribution techniques. We investigate the H I clustering properties relevant for future 21 cm intensity mapping (IM) experiments, including the H I bias and the shot-noise level. The H I bias increases with redshift and it is roughly flat on the largest scales probed. The scale dependence is found at progressively larger scales with increasing redshift, apart from a dip feature at z = 0. The shot-noise values are consistent with the ones inferred by independent studies, confirming that shot noise will not be a limiting factor for IM experiments. We detail the contribution from various galaxy properties on the H I power spectrum and their relation to the halo bias. We find that H I poor satellite galaxies play an important role at the scales of the one-halo term. Finally, we present the 21 cm signal in redshift space, a fundamental prediction to be tested against data from future radio telescopes such as Square Kilometre Array.
- Publication:
-
Monthly Notices of the Royal Astronomical Society
- Pub Date:
- April 2020
- DOI:
- 10.1093/mnras/staa604
- arXiv:
- arXiv:1909.02242
- Bibcode:
- 2020MNRAS.493.5434S
- Keywords:
-
- methods: numerical;
- galaxies: evolution;
- galaxies: intergalactic medium;
- large-scale structure of Universe;
- Astrophysics - Cosmology and Nongalactic Astrophysics;
- Astrophysics - Astrophysics of Galaxies
- E-Print:
- 21 pages, 20 figures, comments welcome