Mild evolution of the stellar metallicity gradients of disc galaxies
  The metallicity gradients of the stellar populations in disc galaxies and
their evolution store relevant information on the disc formation history and on
those processes which could mix stars a posteriori, such as migration, bars
and/or galaxy-galaxy interactions. We aim to investigate the evolution of the
metallicity gradients of the whole stellar populations in disc components of
simulated galaxies in a cosmological context. We analyse simulated disc
galaxies selected from a cosmological hydrodynamical simulation that includes
chemical evolution and a physically motivated Supernova feedback capable of
driving mass-loaded galactic winds. We detect a mild evolution with redshift in
the metallicity slopes of $-0.02 \pm 0.01$ dex~kpc$^{-1}$ from $z\sim 1$. If
the metallicity profiles are normalised by the effective radius of the stellar
disc, the slopes show no clear evolution for $z < 1$, with a median value of
approximately $-0.23$ dex ~$r_{\rm reff}^{-1}$. As a function of stellar mass,
we find that metallicity gradients steepen for stellar masses smaller than
$\sim 10^{10.3} {\rm M_{\odot}}$ while the trend reverses for higher stellar
masses, in the redshift range $z=[0,1]$. Galaxies with small stellar masses
have discs with larger $r_{\rm reff}$ and flatter metallicity gradients than
expected. We detect migration albeit weaker than in previous works. Our stellar
discs show a mild evolution of the stellar metallicity slopes up to $z\sim 1,$
which is well-matched by the evolution calculated archeologically from the
abundance distributions of mono-age stellar populations at $z\sim 0$. Overall,
Supernova feedback could explain the trends but an impact of migration can not
be totally discarded. Galaxy-galaxy interactions or small satellite accretions
can also contribute to modify the metallicity profiles in the outer parts.
[abridged]
