Weighing the Milky Way - investigating the Galactic mass distribution with the outer-halo globular clusters and their tidal tails

• Applicant: Dr. Andreas Küpper
• Subject Area: Astrophysics and Astronomy
• Term: Funded in 2013
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 232615362

The Milky Way is the only spiral galaxy in the Universe that we can investigate from a unique perspective: from the inside. The major research field of Galactic astronomy therefore solely focuses on the understanding of our home galaxy by observations and theory. In this research field, the distribution of mass within the Galaxy represents the vital link between observational findings and theoretical models. However, determinations of the Galactic mass distribution are still very uncertain, especially measurements of the mass and shape of the Galactic dark halo, which dominates the mass distribution at large Galactic radii. Our objective is to measure the Galactic mass distribution out to large Galactic radii by utilizing globular clusters and their tidal tails as tracers of the dark halo mass. We specifically aim at using globular clusters in the outer halo of the Galaxy for studying the shape of the Galactic dark halo, as we find them to be ideally suited for this purpose. We will determine the clusters' orbits to unprecedented precision by fitting numerical simulations to observational data of the clusters and their tidal tails. Precise knowledge of the orbit of a globular cluster allows us to directly infer details on the enclosed mass at the Galactic radius of the respective cluster. In this context, we will also make use of dynamical information, which is encoded in the tidal tails of the clusters and which has not been used for this purpose before. To make use of this unique information, we are going to apply our new and efficient method for generating numerical models of tidal tails. The proposed project will bring together our theoretical expertise on the tidal tails of globular clusters and our observational expertise on the dynamics of outer-halo clusters. We will combine our recently developed numerical methods and a broad variety of new observational data. Hence, we expect a strong synergy form this collaboration. Moreover, due to the relevance of the mass distribution within the Galaxy for the field of Galactic astronomy, we expect our results to have a major impact to the astrophysical community. The mass distribution is of utmost importance for reconstructing the formation history of our Galaxy and for understanding the nature of the Galaxy's dark halo. Ultimately, knowing the mass distribution of our Galaxy even allows for testing scenarios of cosmological structure formation.

• DFG Programme: Research Fellowships
• International Connection: USA
• Host: Professorin Marla Geha, Ph.D.