The Mass Dependence of the Fundamental Metallicity Relation in Cosmological Simulations

The gas-phase metallicity of a galaxy is a direct tracer of its evolutionary history. A galaxy accretes gas, forms new stars, and then increases its metallicity content as those stars die and return metals to the interstellar medium. This is an observationally-found relation between the stellar mass, star formation rate (SFR), and metallicity of galaxies called the Fundamental Metallicity Relation (FMR). It has been theorized that galaxies generally follow the FMR; however, recent work from simulations has suggested a redshift-dependency. Using data from the EAGLE, SIMBA, Illustris, and IllustrisTNG cosmological simulations, we show there is an additional mass component to the FMR. Specifically, an increase in slope around a stellar mass of 10^{9.5} M_⊙ points to the presence of active galactic nuclei (AGN) feedback interaction. This indicates that our understanding of the galactic gas accretion cycle described above needs to be modified to accommodate the AGN feedback.