Radial distribution of stars, gas and dust in SINGS galaxies. III.
  Modeling the evolution of the stellar component in galaxy disks
  (Abridged) We analyze the evolution of 42 spiral galaxies in the Spitzer
Infrared Nearby Galaxies Survey, using extinction-corrected UV, optical and
near-infrared radial profiles to probe the emission of stars of different ages
as a function of radius. We fit these profiles with models that describe the
chemical and spectro-photometric evolution of spiral disks within a
self-consistent framework. These backward models succesfully reproduce the
multi-wavelength profiles of our galaxies, except the UV profiles of some
early-type disks. From the model fitting we infer the maximum circular velocity
of the rotation curve (Vc) and the dimensionless spin parameter (lambda). The
values of Vc are in good agreement with the velocities measured in HI rotation
curves. While our sample is not volume-limited, the resulting distribution of
spins is close to the lognormal function obtained in cosmological N-body
simulations, peaking at ~0.03 regardless of the total halo mass. We do not find
any evident trend between spin and Hubble type, besides an increase in the
scatter for the latest types. According to the model, galaxies evolve along a
roughly constant mass-size relation, increasing their scale-lengths as they
become more massive. The radial scale-length of most disks in our sample seems
to have increased at a rate of 0.05-0.06 kpc/Gyr, being now 20-25% larger than
at z=1.
