Diffuse gas properties and stellar metallicities in cosmological
  simulations of disc galaxy formation
  We analyse the properties of the circum-galactic medium and the metal content
of the stars comprising the central galaxy in eight hydrodynamical `zoom-in'
simulations of disc galaxy formation. We use these properties as a benchmark
for our model of galaxy formation physics implemented in the moving-mesh code
AREPO, which succeeds in forming quite realistic late-type spirals in the set
of `Aquarius' initial conditions of Milky Way-sized haloes. Galactic winds
significantly influence the morphology of the circum-galactic medium and induce
bipolar features in the distribution of heavy elements. They also affect the
thermodynamic properties of the circum-galactic gas by supplying an energy
input that sustains its radiative losses. Although a significant fraction of
the heavy elements are transferred from the central galaxy to the halo, and
even beyond the virial radius, enough metals are retained by stars to yield a
peak in their metallicity distributions at about $Z_{\odot}$. All our default
runs overestimate the stellar [O/Fe] ratio, an effect that we demonstrate can
be rectified by an increase of the adopted SN type Ia rate. Nevertheless, the
models have difficulty in producing stellar metallicity gradients of the same
strength as observed in the Milky Way.
