The role of Star Formation in the evolution of spiral galaxies

Abstract

Spiral galaxies offer a unique opportunity to study the role of star formation in galaxy evolution and to test various theoretical star formation schemes. I review some recent relevant work on the evolution of spiral galaxies. Detailed models are used for the chemical and spectrophotometric evolution, with metallicity dependent stellar yields, tracks and spectra. The models are ``calibrated'' on the Milky Way disk and generalised to other spirals with some simple scaling relations, obtained in the framework of Cold Dark Matter models for galaxy formation. The results compare favourably to the main observables of present day spirals, provided a crucial assumption is made: massive disks form their stars earlier than low mass ones. It is not clear whether this picture is compatible with currently popular hierarchical models of galaxy evolution. The resulting abundance gradients are found to be anticorrelated to the disk scalelength, support radially dependent star formation efficiencies and point to a kind of ``homologuous evolution'' for spirals.