Toward Resolution Convergence for Star Formation and Galactic Winds in Galaxy Simulations

The predictive power of hydrodynamic simulations of galaxies is often hampered by the resolution dependence of subgrid models for star formation (SF) and stellar feedback. We present 3D hydrodynamic simulations of an M82-like low-mass starburst galaxy at resolutions of 4–32 pc and develop optimized subgrid prescriptions to mitigate these numerical inconsistencies. For SF, we adopt a ∼20 pc physical-scale control volume, corresponding to the typical size of giant molecular clouds (GMCs), for gas accretion onto sink particles, reducing its dependence on numerical resolution. We further incorporate an empirical, resolution- and density-dependent SF scheme that accounts for variations in gas surface density across spatial scales, as suggested by observations. Furthermore, we refine the supernova feedback coupling by anchoring the injection volume to the physical cooling radius of the supernova remnant ( R cool ) and utilizing a resolution-dependent thermal-to-kinetic energy partition. These improvements substantially enhance convergence across 4–32 pc: variations in the total stellar mass formed and kinetic energy are reduced to ∼20%, while relative errors in the cool-phase mass outflow rate and integrated X-ray luminosity decrease to below ∼40%. The warm and hot outflow phases remain less well converged, with variations of ∼50% and ∼75%, respectively. The upgraded model also improves the convergence of normalized wind properties, with relative errors below ∼50%, ∼80%, and ∼20% for the time-averaged mass-loading factor, energy-loading factor, and X-ray emission efficiency, respectively. Our results provide a practical framework for achieving more robust simulations of starburst galaxies.