ASymba: HI global profile asymmetries in the Simba simulation

TL;DR

This study uses hydrodynamical simulations to analyze HI profile asymmetries in galaxies, revealing correlations with galaxy properties and validating methods for future large-scale HI surveys.

Contribution

First application of Simba simulations to study HI profile asymmetries, developing methodology and providing initial results for future observational comparisons.

Findings

HI mass correlates strongly with asymmetry measures

Galaxies with asymmetric profiles have lower HI fractions

Asymmetry detection improves with higher HI mass

Abstract

Asymmetry in the spatially integrated, 1D HI global profiles of galaxies can inform us on both internal (e.g. outflows) and external (e.g. mergers, tidal interactions, ram pressure stripping) processes that shape galaxy evolution. Understanding which of these primarily drive HI profile asymmetry is of particular interest. In the lead-up to SKA pathfinder and SKA HI emission surveys, hydrodynamical simulations have proved to be a useful resource for such studies. Here we present the methodology behind, as well as first results, of ASymba: Asymmetries in HI of Simba galaxies, the first time this simulation suite has been used for this type of study. We generate mock observations of the HI content of these galaxies and calculate the profile asymmetries using three different methods. We find that $M_{\rm HI}$ has the strongest correlation with all asymmetry measures, with weaker correlations also found with the number of mergers a galaxy has undergone, and gas and galaxy rotation. We also find good agreement with the xGASS sample, in that galaxies with highly asymmetric profiles tend to have lower HI gas fractions than galaxies with symmetric profiles, and additionally find the same holds in sSFR parameter space. For low HI mass galaxies, it is difficult to distinguish between asymmetric and symmetric galaxies, but this becomes achievable in the high HI mass population. These results showcase the potential of ASymba and provide the groundwork for further studies, including comparison to upcoming large HI emission surveys.