Chemical evolution in our galaxy during the last 5 Gyr

A significant fraction of the gas in the Galactic disk comes from quasi-continuous infall of external material that is moderately processed by stellar nucleosynthesis. Based on a comparison of the abundances in the protosolar cloud (PSC) and the Local Interstellar Cloud (LIC), we propose that the infalling matter carries the nucleosynthetic signature of dwarf galaxies. The dwarfs have low metallicity, and secondary products of stellar nucleosynthesis are scarce as compared to primary products. Using a simple model, we show that the differences found in the LIC and PSC compositions can be explained by adding material processed in dwarf galaxies to the material processed in the Galactic disk. Moreover, some previously unexplained composition observations in the Galaxy, such as the apparently anomalously high metallicity of the Sun, or the "O-18 puzzle" could be resolved in this way.