A model for the formation, evolution and structure of the solar cylinder

Models of the formation, evolution and structure of the solar cylinder are constructed on the basis of a large set of observational data on mainly late-type stars. Star formation in the disc is modelled with a simple, phenomenological prescription of the Schmidt type: Σ#78 * ∞Σ g N , N = 1-2. Models with a threshold for star formation are also considered. Infall of halo gas is assumed to happen on a characteristic time-scale t i . The results obtained are largely independent of the star formation prescription. For the best-fitting model (N = 1), we find that the age of the solar cylinder is t 0 = 11.8 ± 1.0 Gyr and that t i = 3.4 ± 0.4 Gyr