The nature of late-type spiral galaxies: structural parameters, optical
  and near-infrared colour profiles, and dust extinction
  We analyse V and H-band surface photometry of a sample of 18 Sb-Sd galaxies.
Combining high resolution HST images with ground-based NIR observations, we
extract photometric profiles, which cover the whole disk and provide the
highest possible resolution. This is the first photometric study of late-type
spirals for which the stellar kinematics have been measured. For 10 out of the
18 galaxies, HST data in both F160W (H) and F606W (V) are available, and, for
those, we present colour maps and radial colour profiles at the resolution of
the Hubble Space Telescope.
  Colours vary significantly from galaxy to galaxy, but tend to be highly
homogeneous within each galaxy, with smooth and flat colour profiles. Some of
the colour maps show jumps in the inner regions, likely due to dust. We
determine extinction-maps in an almost model-independent way using the V-H
colour map and the SAURON Mg b absorption line map of Ganda et al. (2007). The
maps show that A_V ranges from 0 to 2 mag, in the center from 0 to 1.5 mag, in
agreement with the models of Tuffs et al. (2004).
  We describe the surface brightness profiles as the superposition of an
exponential disk and a Sersic bulge. The bulges are small (0.1-2.5 kpc), and
show a shape parameter n ranging from ~ 0.7 to 3, with a mean value smaller
than two: well below the value for the 'classical' de Vaucouleurs bulges. Most
galaxies (16 out of 18) show a central light excess above the Sersic fit to the
bulge, which can be interpreted as a nuclear cluster, as shown by previous
studies. We provide zero-order estimates for the magnitude of these components.
We discuss the correlations among the structural galaxy parameters and with
other relevant quantities (abridged).
