A stringent test of the galaxy formation paradigm: detailed modeling of the dynamics and stellar population of the Milky Way

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High and low-redshift observations, in combination with numerical simulations, have provided a scenario, over the last 30 years, in which galaxy formation proceeds in a hierarchical fashion, driven by the gravitational collapse of dark matter (DM). Although the scenario explains most of the observations, its strongest and cleanest predictions still have to be confirmed: (i) galaxies are expected to be embedded in massive DM halos, however, remarkably, the very existence of DM is still debated and the possibility that the laws of gravity are not those of Einstein is under discussion. (ii) the hierarchical build up of galaxies is expected to leave behind a very large number of substructures, in both the dark and luminous matter. Although some substructure in nearby galaxies exists, this is not at the expected level. (iii) galaxy formation models make detailed prediction about the age and chemical composition of galactic substructure, but these information are difficult to extract from galaxy observations. Due to its vicinity, our Milky Way constitute a unique laboratory to perform the above stringent observational tests of the galaxy formation paradigm. For our Galaxy in fact individual stars can be easily observed, and position and velocity can in principle be obtained. The stars could be used as tracers of the gravity to accurately detect the presence of DM. The chemical composition of individual stars can also be measured, and could be used, in combination with the stellar kinematics, to uncover stellar subcomponents in the Galaxy. However until now no such data existed. The situation is soon going to change dramatically. A number of ongoing large observational survey from the ground (RAVE, SEGUE) and from space (Gaia) will measure position and velocities for a large fraction of all the stars in our Galaxy. This will provide the biggest improvement in our knowledge of the Galaxy, since Galileo observed it with its telescope, four centuries ago, first realizing that it was actually made of individual stars. The new data have a similar potential to revolutionize our understanding of how galaxies form. The main goal of my proposed project is to perform the above three stringent tests of the galaxy formation paradigm, by constructing a detailed model of the dynamics and the chemical composition of our Milky Way, to be compared with the position, velocity and chemical composition stellar measurements provided by the RAVE, SEGUE and then Gaia survey.