# The physical drivers of the atomic hydrogen-halo mass relation

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7 Citations (Scopus)

## Abstract

We use the state-of-The-Art semi-Analytic galaxy formation model, shark, to investigate the physical processes involved in dictating the shape, scatter, and evolution of the Hi-halo mass (HIHM) relation at 0 ≤ z ≤ 2. We compare shark with Hi clustering and spectral stacking of the HIHM relation derived from observations finding excellent agreement with the former and a deficiency of Hi in shark at Mvir ≈ 1012-13 M in the latter. In shark, we find that the Hi mass increases with the halo mass up to a critical mass of ≈1011.8 M; between ≈1011 and 1013 M, the scatter in the relation increases by 0.7 dex and the Hi mass decreases with the halo mass on average (till, after which it starts increasing); at, the Hi content continues to increase with increasing halo mass, as a result of the increasing Hi contribution from satellite galaxies. We find that the critical halo mass of ≈1012 M is set by feedback from active galactic nuclei (AGNs) which affects both the shape and scatter of the HIHM relation, with other physical processes playing a less significant role. We also determine the main secondary parameters responsible for the scatter of the HIHM relation, namely the halo spin parameter at ${M}_{\rm vir}\, \lt$ 1011.8 M, and the fractional contribution from substructure to the total halo mass for 1013 M. The scatter at 1011.8 M 1013 M is best described by the black hole-To-stellar mass ratio of the central galaxy, reflecting the relevance of AGN feedback. We present a numerical model to populate dark matter-only simulations with Hi at 0 ≤ z ≤ 2 based solely on halo parameters that are measurable in such simulations.

Original language English 44-67 24 Monthly Notices of the Royal Astronomical Society 498 1 https://doi.org/10.1093/mnras/staa2251 Published - 1 Oct 2020

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