Correlations between mass, stellar kinematics and gas metallicity in
  EAGLE galaxies
  The metallicity of star-forming gas in galaxies from the EAGLE 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 $M_\star\approx 10^{10}~{\rm M}_\odot$.
This trend inverts at higher values of $M_\star$, 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
anti-correlation 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 play a dominant role.
