Colours and luminosities of z=0.1 simulated galaxies in the EAGLE
  simulations
  We calculate the colours and luminosities of redshift z = 0.1 galaxies from
the EAGLE simulation suite using the GALAXEV population synthesis models. We
take into account obscuration by dust in birth clouds and diffuse ISM using a
two-component screen model, following the prescription of Charlot and Fall. We
compare models in which the dust optical depth is constant to models where it
depends on gas metallicity, gas fraction and orientation. The colours of EAGLE
galaxies for the more sophisticated models are in broad agreement with those of
observed galaxies. In particular, EAGLE produces a red sequence of passive
galaxies and a blue cloud of star forming galaxies, with approximately the
correct fraction of galaxies in each population and with g-r colours within 0.1
magnitudes of those observed. Luminosity functions from UV to NIR wavelengths
differ from observations at a level comparable to systematic shifts resulting
from a choice between Petrosian and Kron photometric apertures. Despite the
generally good agreement there are clear discrepancies with observations. The
blue cloud of EAGLE galaxies extends to somewhat higher luminosities than in
the data, consistent with the modest underestimate of the passive fraction in
massive EAGLE galaxies. There is also a moderate excess of bright blue galaxies
compared to observations. The overall level of agreement with the observed
colour distribution suggests that EAGLE galaxies at z = 0.1 have ages,
metallicities and levels of obscuration that are comparable to those of
observed galaxies.
