Study of the stellar population properties in the discs of ten spiral
  galaxies
  We investigated the properties of the stellar populations in the discs of a
sample of ten spiral galaxies. Our analysis focused on the galaxy region where
the disc contributes more than 95 per cent of total surface brightness in order
to minimise the contamination of the bulge and bar. The luminosity-weighted age
and metallicity were obtained by fitting the galaxy spectra with a linear
combination of stellar population synthesis models, while the total
overabundance of {\alpha}-elements over iron was derived by measuring the
line-strength indices. Most of the sample discs display a bimodal age
distribution and they are characterised by a total [{\alpha}/Fe] enhancement
ranging from solar and supersolar. We interpreted the age bimodality as due to
the simultaneous presence of both a young (Age$\,\leq\,4$ Gyr) and an old
(Age$\,>\,$4 Gyr) stellar population. The old stellar component usually
dominates the disc surface brightness and its light contribution is almost
constant within the observed radial range. For this reason, no age gradient is
observed in half of the sample galaxies. The old component is slightly more
metal poor than the young one. The metallicity gradient is negative and
slightly positive in the old and young components, respectively. These results
are in agreement with an inside-out scenario of disc formation and suggest a
reduced impact of the radial migration on the stellar populations of the disc.
The young component could be the result of a second burst of star formation in
gas captured from the environment.
