2025MNRAS.540.3047H

We present a study of the neutral atomic hydrogen (H I) content of spatially resolved, low-redshift galaxies in the SIMBA cosmological simulations. We create synthetic H I data cubes designed to match observations from the Apertif Medium-Deep H I imaging survey, and follow an observational approach to derive the H I size-mass relation. The H I size-mass relation for s IMBA is in broad agreement with the observed relation to within 0.1 dex, but SIMBA galaxies are slightly smaller than expected at fixed H I mass. We quantify the H I spectral ($\rm{A_{\rm{flux}}}$) and morphological ($\rm{A_{\rm{mod}}}$) asymmetries of the galaxies and motivate standardizing the relative spatial resolution when comparing $\rm{A_{\rm{mod}}}$ values in a sample that spans several orders of magnitude in H I mass. Galaxies are classified into three categories (isolated, interacted, or merged) based on their dynamical histories over the preceding $\sim$2 Gyr to contextualize disturbances in their H I reservoirs. We determine that the interacted and merged categories have higher mean asymmetries than the isolated category, with a larger separation between the categories' $\rm{A_{\rm{mod}}}$ distributions than between their $\rm{A_{\rm{flux}}}$ distributions. For the interacted and merged categories, we find an inverse correlation between baryonic mass and $\rm{A_{\rm{mod}}}$ that is not observed between baryonic mass and $\rm{A_{\rm{flux}}}$. These results, coupled with the weak correlation found between $\rm{A_{\rm{flux}}}$ and $\rm{A_{\rm{mod}}}$, highlight the limitations of only using $\rm{A_{\rm{flux}}}$ to infer the H I distributions of spatially unresolved H I detections.