Chemical evolution models of Local Group galaxies

Summary

Status quo and perspectives of standard chemical evolution models of Local Group galaxies are summarized, and what we have learned from them is discussed, as well as what we have not learned yet, and what I think will be learned in the near future. Galactic chemical evolution models have shown that: i) stringent constraints on primordial nucleosynthesis can be derived from the observed Galactic abundances of the light elements; ii) the Milky Way has been accreting external gas from early epochs to the present time; and iii) the vast majority of Galactic halo stars have formed quite rapidly at early epochs. Chemical evolution models for the closest dwarf galaxies, although still uncertain, are expected to become extremely reliable in the immediate future, thanks to the quality of new generation photometric and spectroscopic data which are currently being acquired.

Introduction

The proximity of Local Group galaxies makes them the ideal benchmarks to study galaxy formation and evolution, because they are the only systems where the accuracy and the wealth of observational data allows us to understand them in a sufficiently reliable way. In fact, to understand the evolution of galaxies, astronomers must follow two distinct and complementary approaches: on one hand they must develop theoretical models of galaxy formation, of chemical and dynamical evolution, and on the other hand, they must collect accurate observational data to constrain the models. It is of particular importance to acquire reliable data on chemical abundances, masses and kinematics of galactic components (gas, stars, dark matter), star formation (SF) regimes, and stellar initial mass function (IMF)—quantities that are best derived in nearby systems.