Star formation rates and abundance gradients in disk galaxies

We present analytic models for the evolution of disk galaxies, placing special emphasis on the radial properties. Our models are straightforward extensions of the original Schmidt models, with a dependence of star formation rate on gas density. Here we introduce an additional parameter, the local angular frequency, and are careful to distinguish between atomic and molecular gas. The models provide successful descriptions of several measures of galactic disk evolution, including solar neighborhood chemical evolution, the presence and amplitude of metallicity and color gradients in disk galaxies, and the global rates of star formation in disk galaxies, and aid our understanding of the apparent connection between young and old stellar populations in spiral galaxies.