Evolution of spiral galaxies .4. Radial distributions of abundances in external galaxies

The multiphase model of Ferrini and coworkers has been used to study the evolution of six spiral galaxies of different morphological types. This kind of model has been successfully applied to describe the chemical evolution of the solar neighborhood, the whole Galactic disk, and the bulge of the Galaxy in the first five papers of this series. The present study constitutes an extension of our previous work to spiral galaxies other than our own, with a twofold goal: the investigation of the possible relation between the chemical evolution of galaxies and their classification, and the possibility of applying a unique evolutionary scheme to all galaxies. The comparison of results with the observed abundance gradients indicates that these are determined by a fundamental imprint that arises from an early phase of the evolution of a given galaxy: the initial mass of the protogalaxy and its spatial distribution. This suggests a connection between the present abundance gradient and the formation process of a spiral galaxy through the collapse of material forming the disk.