The galaxy HI-(sub)halo connection and the HI spatial clustering of local galaxies

We extend the local stellar galaxy-(sub)halo connection to the atomic hydrogen (H I) component by seeding semi-empirically galaxies into a large N-body dark matter (DM) simulation. The main input to construct the mock galaxy catalogue are: our constrained stellar mass-to-(sub)halo circular velocity (M-*-V-DM) relation, assuming a scatter independent of any galaxy property, and the empirical M-HI conditional probability distributions given M-* for central and satellite galaxies. We find that the < logM(HI)> - log M-DM relation is not a monotonic increasing function. It increases with mass up to M-DM greater than or similar to 10(12) M-circle dot, attaining a maximum of < log(M-HI/M-circle dot)> similar to 9.2, and at higher (sub)halomasses, < log(M-HI)> decreases slightly with MDM. The scatter around it is also large and mass dependent. The bivariate M-HI and M-DM distribution is broad and bimodal, specially at M-DM greater than or similar to 10(12) M-circle dot, which is inherited from the input M-HI conditional distributions. We also report the total (central+satellites) HI gas mass within haloes, M-HI(tot), as a function of MDM. The mean M-HI(tot)-MDM relation is an increasing monotonic function. The galaxy spatial clustering increases weakly as the M-HI threshold increases. Our HI mock galaxies cluster more in comparison to the blind HI ALFALFA (Arecibo Fast Legacy ALFA) survey but we show that it is mainly due to the selection effects. We discuss the implications of our results in the light of predictions from semi-analytical models and hydrodynamics simulations of galaxy evolution.

Automated summary

By seeding semi-empirical galaxies into a large N-body dark matter simulation, we extend the local stellar galaxy-(sub)halo connection to the atomic hydrogen component. The relation between the atomic hydrogen mass and dark matter mass is not a monotonic increasing function, but rather increases within a certain mass range before slightly decreasing. The bivariate distribution of atomic hydrogen and dark matter mass is broad and bimodal, impacted by the initial conditions.