How Metals Are Transported Into and Out of a Galactic Disk: Dependence on Hydrodynamic Schemes in Numerical Simulations

Metallicity is a fundamental probe for understanding the baryon physics in a galaxy. Since metals are intricately associated with radiative cooling, star formation, and stellar feedback, reproducing the observed metal distribution through numerical experiments will provide a prominent way to examine our understanding of galactic baryon physics. In this study, we analyze the dependence of the galactic metal distribution on numerical schemes and quantify the differences in metal mixing among modern galaxy simulation codes (the mesh-based code Enzo and the particle-based codes Gadget-2 and Gizmo-PSPH). In particular, we examine different stellar feedback strengths and an explicit metal diffusion scheme in particle-based codes, as a way to alleviate the well-known discrepancy in metal transport between mesh-based and particle-based simulations. We demonstrate that a sufficient number of gas particles are needed in the gas halo to properly investigate the metal distribution therein. Including an explicit metal diffusion scheme does not significantly affect the metal distribution in the galactic disk but does change the amount of low-metallicity gas in a hot diffuse halo. We also find that the spatial distribution of metals depends strongly on how the stellar feedback is modeled. We demonstrate that the previously reported discrepancy in metals between mesh-based and particle-based simulations can be mitigated with our proposed prescription, enabling these simulations to be reliably utilized in the study of metals in galactic halos and the circumgalactic medium.

Automated summary

Metallicity is an important factor in understanding the baryon physics in galaxies, and reproducing observed metal distribution through numerical experiments is crucial. This study examines the impact of numerical schemes on galactic metal distribution and finds that a sufficient number of gas particles is needed in particle-based simulations to properly investigate metal distribution. The inclusion of an explicit metal diffusion scheme does not significantly affect metal distribution in the galactic disk.