Abstract

Chemical abundances in stars and gas and their ratios are useful tools to impose constraints either on stellar nucleosynthesis or galaxy formation timescales. There are particular abundances ratios, such as for example [Alpha/Fe] and [N/O], which can be used as cosmic clocks. I will review successful models of galactic chemical evolution which enable us to reconstruct the star formation history of a galaxy just by reproducing the observed stellar and gas abundances and abundance ratios. I will show that this astro-archaeological approach has been successful in explaining the abundances in different galaxy types. In particular, I will discuss the chemical evolution of the Milky Way, the dwarf spheroidals of the Local Group and elliptical galaxies and the constraints we can impose on their evolutionary history, and in particular on the timescales of their formation. I will demonstrate that the history of star formation of a galaxy is the main driver of its evolution and that chemical abundances in some cases suggest modalities of galaxy formation which differ from the predictions of hierarchical galaxy evolution models.