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The Galactic halo: formation history and dynamics

PhD ceremony:Mr H.H. (Helmer) Koppelman
When:September 18, 2020
Supervisors:prof. dr. A. (Amina) Helmi, prof. dr. E. (Eline) Tolstoy
Where:Academy building RUG
Faculty:Science and Engineering

The Milky Way, the galaxy in which we live, knows a rich history that can be traced back to billions of years ago. By studying the motions and chemical compositions of its stars we aim to identify the major events that shaped our Galaxy. Moreover, because the motions of the stars are driven by the gravitational force, we can use them to infer the amount and distribution of the (dark) mass in the Milky Way.

One of the major discoveries cover in this thesis is that the Milky Way merged with another galaxy some 10 billion years ago. The revelation of this discovery is not the merger itself, which are fairly common for galaxies, but the size of the other galaxy. We expected to find evidence for several smaller galaxies, but instead found evidence for mainly one large galaxy.Besides the history, we also present a model that aims to describe the interaction between stellar streams and dark matter substructures, and also determine the mass of the Milky Way based on the motion of nearby stars.