2025MNRAS.543.4286B

The gas-phase metallicity affects heating and cooling processes in the star-forming galactic interstellar medium (ISM) as well as ionizing luminosities, wind strengths, and lifetimes of massive stars. To investigate its impact, we conduct magnetohydrodynamic simulations of the ISM using the FLASH code as part of the SILCC project. The simulations assume a gas surface density of 10 M$_\odot$ pc$^{-2}$ and span metallicities from 1/50 to 1 Z$_\odot$. We include non-equilibrium thermochemistry, a space- and time-variable far-UV background and cosmic ray ionization rate, metal-dependent stellar tracks, the formation of H II regions, stellar winds, type II supernovae, and cosmic ray injection and transport. With the metallicity decreasing over the investigated range, the star formation rate decreases by more than a factor of 10, the mass fraction of cold gas decreases from 60 per cent to 2.3 per cent, while the volume filling fraction of the warm gas increases from 20 per cent to 80 per cent. Furthermore, the fraction of H$_\mathrm{2}$ in the densest regions drops by a factor of 4, and the dense ISM fragments into approximately five times fewer structures at the lowest metallicity. Outflow mass loading factors remain largely unchanged, with values close to unity, except for a significant decline at the lowest metallicity. Including the major processes that regulate ISM properties, this study highlights the strong impact of gas phase metallicity on the star-forming ISM.