The shape of oxygen abundance profiles explored with MUSE: evidence for
  widespread deviations from single gradients
  We characterise the oxygen abundance radial distribution of a sample of 102
spiral galaxies observed with VLT/MUSE using the O3N2 calibrator. The high
spatial resolution of the data allows us to detect 14345 HII regions with the
same image quality as with photometric data, avoiding any dilution effect. We
develop a new methodology to automatically fit the abundance radial profiles,
finding that 55 galaxies of the sample exhibit a single negative gradient. The
remaining 47 galaxies also display, as well as this negative trend, either an
inner drop in the abundances (21), an outer flattening (10) or both (16), which
suggests that these features are a common property of disc galaxies. The
presence and depth of the inner drop depends on the stellar mass of the
galaxies with the most massive systems presenting the deepest abundance drops,
while there is no such dependence for the outer flattening. We find that the
inner drop appears always around $\rm 0.5\,r_e$, while the position of the
outer flattening varies over a wide range of galactocentric distances.
Regarding the main negative gradient, we find a characteristic slope of
$\alpha_{O/H} = -\,0.10\pm0.03\,\rm{dex}/r_e$. This slope is independent of the
presence of bars and the density of the environment. However, when inner drops
or outer flattenings are detected, slightly steeper gradients are observed.
This suggests that radial motions might play an important role in shaping the
abundance profiles. We define a new normalisation scale ($r_{O/H}$) for the
radial profiles based on the characteristic abundance gradient, with which all
the galaxies show a similar position for the inner drop ($\sim0.5\,r_{O/H}$)
and the outer flattening ($\sim1.5\,r_{O/H}$).Finally, we find no significant
dependence of the dispersion around the negative gradient with any galaxy
property, with values compatible with the uncertainties of the derived
abundances.
