The Milky Way's disk in the age of Gaia

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I propose to investigate the properties of the Milky Way's disk and from this deduce how our home in the Universe formed and evolved over cosmic time. After a century of detailed study, many of the most basic properties of the Milky Way are still poorly understood. This includes its mass, how this mass is distributed from the center to the outskirts and how much of it is dark matter, how many stars are formed at different epochs and with what chemical properties, and what spiral structure---so clear when we look at other galaxies---looks like in the Milky Way and what effect it has on the motions of stars. New stellar surveys that measure the distances, motions, ages, and chemical abundances of large numbers of stars are being conducted now that will vastly expand the available data for investigating the properties of the Milky Way.******I will determine the spatial, kinematic, and age distributions of stars over a large part of the Milky Way's disk and how these depend on chemical abundances. This will elucidate the processes of star formation, chemical enrichment through feedback from different kinds of stars, and provide us with a detailed picture of the stellar make-up of the disk. I will also use the motions of stars to determine the overall distribution of mass through its gravitational pull on stellar orbits and how this mass is divided into ordinary (stars and gas) and dark matter. Finally, I will investigate the deviations in the stellar motions from simple smooth models for the mass distribution to determine the influence of spiral structure, the central bar, and other kinds of non-axisymmetryc, time-dependent perturbations. Through the combination of these investigations, this work will provide important new insights into the physics of galaxy formation and dark matter.**