Inflow of gas to the solar neighborhood during evolution of the galactic disk

We discuss several lines of evidence indicating that gas is flowing into th e solar neighborhood and go on to offer a theoretical framework to explain this phenomenon, which is important for any model of the chemical and dynam ical evolution of the Galaxy. We derive a theoretical age distribution for the G dwarf stars in the solar neighborhood that fits well the distribution observed recently in the generally increasing trend of the amplitude of os cillation with time, leading to star formation peaks at several epochs. Our model is based on the interference between two effects: the variable rate of gas inflow to the solar vicinity due to the density wave pattern in the disk, and the arrival of gas from the local intergalactic medium broken cyc lically by star formation processes. The model is shown to be consistent wi th a scenario in which low-metallicity gas falls continually to the Galacti c plane from the intergalactic medium, notably in the form of high-velocity clouds.