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Observed and simulated galaxies exhibit correlations between stellar mass, metallicity, and morphology. We use the eagle cosmological simulation to examine the origin of these correlations for galaxies in the stellar mass range |$10^9~\rm {M_\odot } \leqslant \ {\it M}_\star \leqslant 10^{10}~\rm {M_\odot }$|⁠ , and the extent to which they contribute to the scatter in the mass–metallicity relation. We find that rotationally supported disc galaxies have lower metallicity than dispersion supported spheroidal galaxies at a given mass, in agreement with previous findings. In eagle , this correlation arises because discs form stars at later times, redshift |$z \leqslant 1$|⁠ , from the accretion of low-metallicity gas, whereas spheroidal galaxies galaxies typically form stars earlier, mainly by consumption of their gas reservoir. The different behaviour reflects the growth of their host dark matter halo: at a given stellar mass, disc galaxies inhabit dark matter haloes with lower mass that formed later compared to the haloes of spheroidal galaxies. Halo concentration plays a secondary role. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]