Star formation and some aspects of the chemical evolution of the Galaxy

This study aims to develop a consistent model of chemical evolution of the Galaxy, particularly the solar neighborhood, with a view to formulating the star formation rate. The star formation rate is shown to be correlated with the surface density of molecular hydrogen, and to have remained practically constant over the lifetime of the disk. This is explained through a correlation between the molecular hydrogen fraction and the average metallicity of any given region of the disk, which suggests negligible infall and finite initial metallicity. A consistent model is proposed to solve the G-dwarf problem, the metallicity gradient and the stellar age-metallicity relation, leading to the prediction of some initial amount of predisk processing of gas into visible and dark matter. It is found that for a number of reasons the Bhat et al. distribution of molecular hydrogen in the Galaxy is preferable to that given by Sanders, Solomon and Scoville.