Abstract:
To characterize the morphological structure and the stellar populations of a sample of
thirteen spiral galaxies, we analyzed WISE and GALEX images, and constructed pixel
magnitude-magnitude and color-magnitude diagrams. The diagrams reveal groups of pixels
which spatially trace the structural components of the galaxies. The diagrams and radial
surface brightness profiles indicate that variations in the surface mass densities of the old
stellar populations play a major role in the differentiation of structures. We estimate the
ages of the young stellar complexes and the dust extinction in these galaxies by means of
comparison to models of simple stellar populations born from an instantaneous burst. The
study of these properties is possible through the combination of ultraviolet and infrared data
and to the high sensitivity of the ultraviolet colour to variations in age. We observe an
extinction gradient whose slope depend on the presence of a bar or a nuclear activity : the
exctinction decreases with respect to the galactocentric distance and the slope is smaller for
galaxies with a bar or with a nuclear activity. There is an age gradient as well, with the
external regions being less evolved than the central ones, except for the late-type galaxies.
