Galaxy metallicity scaling relations in the EAGLE simulations

We quantify the correlations between gas-phase and stellar metallicities and global properties of galaxies, such as stellarmass, halomass, age and gas fraction, in the Evolution and Assembly of GaLaxies and their Environments suite of cosmological hydrodynamical simulations. The slope of the correlation between stellar mass and metallicity of star-forming (SF) gas (M(*)Z(SF,gas) relation) depends somewhat on resolution, with the higher resolution run reproducing a steeper slope. This simulation predicts a non-zero metallicity evolution, increasing by approximate to 0.5 dex at similar to 10(9) M-circle dot since z = 3. The simulated relation between stellar mass, metallicity and star formation rate at z less than or similar to 5 agrees remarkably well with the observed fundamental metallicity relation. At M-* less than or similar to 10(10.3) M-circle dot and fixed stellar mass, higher metallicities are associated with lower specific star formation rates, lower gas fractions and older stellar populations. On the other hand, at higher M-*, there is a hint of an inversion of the dependence of metallicity on these parameters. The fundamental parameter that best correlates with the metal content, in the simulations, is the gas fraction. The simulated gas fraction-metallicity relation exhibits small scatter and does not evolve significantly since z = 3. In order to better understand the origin of these correlations, we analyse a set of lower resolution simulations in which feedback parameters are varied. We find that the slope of the simulated M-*-Z(SF),(gas) relation is mostly determined by stellar feedback at low stellar masses (M-* less than or similar to 10(10) M-circle dot), and at high masses (M-* less than or similar to 10(10) M-circle dot) by the feedback from active galactic nuclei.