ABSTRACT We study the stellar mass-gas metallicity relation (MZR) which shows a significant scatter for a fixed stellar mass. By defining global environments, nodes, filaments, and voids within the Horizon Run 5 cosmological hydrodynamical simulation, we explore when and where the enrichment of galaxies occurs, analysing key evolution parameters such as star-formation rate and changes in gas-fraction and gas-metallicity per unit time. At high redshift (z 4. 5), there are minimal deviations from the MZR due to environment, however, larger deviations emerge as redshift decreases. Low stellar mass galaxies in nodes, M 10^9. 8\, M, start showing deviations at z = 3. 5, whilst other environments do not. For, z 2, filaments and voids begin to show deviations above and below the MZR, respectively. By z = 0. 625, the last epoch of HR5, deviations exist for all stellar masses and environments, with a maximum value of 0. 13 dex at M 10^9. 35\, M, between the median gas metallicities of node and void galaxies. To explain this environmental variance we discuss gas accretion, AGN, ram-pressure-stripping and strangulation as regulators of Z ₆. Concurrently, at high metallicities, for z 2, while massive galaxies in nodes show increasing Z ₆ and decreasing O/Fe, void galaxies show a turnover where Z ₆ falls with decreasing O/Fe. This directly points to the importance of cold-gas accretion in retaining lower Z ₆ in massive void galaxies for z 2, whilst its absence in nodes allowed Z ₆ to access higher values.
Rowntree et al. (2026) studied this question.