Formation and Evolution of the Milky Way

Abstract

The problem of understanding the formation of the Galaxy is part of the problem of explaining galaxy formation in general. In particular, we should try to understand the relative importance of mergers and dissipative collapse in the formation of all galaxies, and whether the observational information about our Galaxy is enough to explain the timescales and the mechanisms of its formation and if this can be in agreement with currently popular hierarchical merger models. As we will see in what follows, it is from the study of chemical and dynamical properties of the different stellar populations that we can gain information on galactic formation and evolution. In fact, the chemical composition in the atmospheres of main-sequence stars represents, in most cases, the chemical composition of the interstellar medium (ISM) from which the stars were formed. Besides, kinematical properties of the stars contain information about the conditions of the gas at the time of star formation, since the dynamical relaxation time is sufficiently long compared to the age of the Galaxy. Thus the metal abundances and the kinematics of the stars represent important information concerning the history of the chemical and dynamical evolution of the Galaxy. An extensive review of galactic structure surveys can be found in Majewski (1993).