Chemical evolution of two-component galaxies. IV - A generalized model allowing for gas inflow

An attempt is made to incorporate two different types of models into a single chemical-evolution scheme for two-component galaxies: the S models which allow mass conservation, and the I models which allow initial zero masses and no mass conservation due to gas inflow. If the stellar birthrate function is assumed to be a universal law, the chemical evolution of the Galactic disk may be understood in terms of different zones (which can be represented as concentric and coaxial rings) the total density of which decreases monotonically, owing to a corresponding decrease in total mass and/or increase in volume, when passing from the center to the border of the disk. Concerning the Galactic spheroidal component, it is found that only S models with massive halos are able to acceptably reproduce the empirical metal abundance distribution.