The origin of the enhanced metallicity of satellite galaxies
  Observations of galaxies in the local Universe have shown that both the
ionized gas and the stars of satellites are more metal-rich than of equally
massive centrals. To gain insight into the connection between this metallicity
enhancement and other differences between centrals and satellites, such as
their star formation rates, gas content, and growth history, we study the
metallicities of >3600 galaxies with M_star > 10^10 M_sun in the cosmological
hydrodynamical EAGLE 100 Mpc `Reference' simulation, including ~1500 in the
vicinity of galaxy groups and clusters (M_200 >= 10^13 M_sun). The simulation
predicts excess gas and stellar metallicities in satellites consistent with
observations, except for stellar metallicities at M_star <~ 10^10.2 M_sun where
the predicted excess is smaller than observed. The exact magnitude of the
effect depends on galaxy selection, aperture, and on whether the metallicity is
weighted by stellar mass or luminosity. The stellar metallicity excess in
clusters is also sensitive to the efficiency scaling of star formation
feedback. We identify stripping of low-metallicity gas from the galaxy
outskirts, as well as suppression of metal-poor inflows towards the galaxy
centre, as key drivers of the enhancement of gas metallicity. Stellar
metallicities in satellites are higher than in the field as a direct
consequence of the more metal-rich star forming gas, whereas stripping of stars
and suppressed stellar mass growth, as well as differences in accreted vs.
in-situ star formation between satellites and the field, are of secondary
importance.
