Arm and interarm abundance gradients in CALIFA spiral galaxies
  Spiral arms are the most singular features in disc galaxies. These structures
can exhibit different patterns, namely grand design and flocculent arms, with
easily distinguishable characteristics. However, their origin and the
mechanisms shaping them are unclear. The overall role of spirals in the
chemical evolution of disc galaxies is another unsolved question. In
particular, it has not been fully explored if the \hii\,regions of spiral arms
present different properties from those located in the interarm regions. Here
we analyse the radial oxygen abundance gradient of the arm and interarm star
forming regions of 63 face-on spiral galaxies using CALIFA Integral Field
Spectroscopy data. We focus the analysis on three characteristic parameters of
the profile: slope, zero-point, and scatter. The sample is morphologically
separated into flocculent versus grand design spirals and barred versus
unbarred galaxies. We find subtle but statistically significant differences
between the arm and interarm distributions for flocculent galaxies, suggesting
that the mechanisms generating the spiral structure in these galaxies may be
different to those producing grand design systems, for which no significant
differences are found. We also find small differences in barred galaxies, not
observed in unbarred systems, hinting that bars may affect the chemical
distribution of these galaxies but not strongly enough as to be reflected in
the overall abundance distribution. In light of these results, we propose bars
and flocculent structure as two distinct mechanisms inducing differences in the
abundance distribution between arm and interarm star forming regions.
