The physical drivers of the atomic hydrogenhalo mass relation
Abstract
We use SHARK, a semianalytic galaxy formation model, to investigate the physical processes involved in dictating the shape, scatter and evolution of the HIhalo mass relation at $0\leq z \leq 2$. We compare SHARK with HI clustering and spectral stacking of the HIhalo mass relation derived from observations finding excellent agreement with the former and a deficiency of HI in SHARK at $M_{\rm vir}\approx 10^{1213} M_{\odot}$ in the latter, but otherwise great agreement below and above that mass threshold. In SHARK, we find that the HI mass increases with the halo mass up to a critical mass of $\approx 10^{11.8} M_{\odot}$; between $\sim 10^{11.8}10^{13}M_{\odot}$, the scatter in the relation increases by 0.7 dex and the HI mass decreases with the halo mass on average; at $M_{\rm vir} \geq 10^{13} M_{\odot}$, the HI content continues to increase with halo mass. We find that the critical halo mass of $\approx 10^{12} M_{\odot}$ is largely set by feedback from Active Galactic Nuclei (AGN), and the exact shape and scatter of the HIhalo mass relation around that mass is extremely sensitive to how AGN feedback is modelled, with other physical processes playing a less significant role. We determine the main secondary parameters responsible for the scatter of the HIhalo mass relation, namely the halo spin parameter at $M_{\rm vir}\leq 10^{11.8} M_{\odot}$, and the fractional contribution from substructure to the total halo mass for $M_{\rm vir}\geq 10^{13} M_{\odot}$. The scatter at $10^{11.8}<M_{\rm vir}<10^{13} M_{\odot}$ is best described by the blackholetostellar mass ratio of the central galaxy, reflecting the AGN feedback relevance. We present a numerical model to populate dark matteronly simulations with HI at $0\leq z \leq 2$ based solely on halo parameters that are measurable in such simulations.
 Publication:

arXiv eprints
 Pub Date:
 June 2020
 arXiv:
 arXiv:2006.12102
 Bibcode:
 2020arXiv200612102C
 Keywords:

 Astrophysics  Astrophysics of Galaxies
 EPrint:
 Submitted to MNRAS