Correlations between mass, stellar kinematics, and gas metallicity in EAGLE galaxies

The metallicity of star-forming gas in galaxies from the EAGLE (Evolution and Assembly of GaLaxies and their Environments) simulations increases with stellar mass. Here, we investigate whether the scatter around this relation correlates with morphology and/or stellar kinematics. At redshift z = 0, galaxies with more rotational support have lower metallicities on average when the stellar mass is below M_⋆ ≈ 10¹⁰ M_⊙. This trend inverts at higher values of M_⋆, when prolate galaxies show typically lower metallicity. At increasing redshifts, the trend between rotational support and metallicity becomes weaker at low stellar mass but more pronounced at high stellar mass. We argue that the secondary dependence of metallicity on stellar kinematics is another manifestation of the observed anticorrelation between metallicity and star formation rate at a given stellar mass. At low masses, such trends seem to be driven by the different star formation histories of galaxies and stellar feedback. At high masses, feedback from active galactic nuclei and galaxy mergers plays a dominant role.