GalCenSus -GALactic CENter Structures Under Scrutiny

Our own Galaxy, the Milky Way, is a barred spiral galaxy, with similar properties to other galaxies. It has several spiral arms, that coalesce in a bar-shaped central region. Within this bar is the Galactic Centre, which stands out from the rest of the Milky Way in several ways: It hosts the closest supermassive black hole to us, has the highest concentration of stars (several tens of millions of stars), confined to a small region (<1% of the entire Milky Way), and some of these stars have a higher abundance of heavy elements (i.e. metallicity) than stars anywhere else in the Milky Way. The Galactic Centre is like a melting pot for stars: They have a wide range of ages and chemical compositions, and different places of origin. Many of the stars formed directly from gas in the Galactic Centre, but others formed elsewhere in star clusters and then migrated inwards. Yet, not all the gas in the Galactic Centre forms stars and some gas is likely consumed by the supermassive black hole. How and when the gas (that later formed stars or fed the supermassive black hole) and the migrated stars were brought to the Galactic Centre, are still open questions. By studying the stars and their history, we can also constrain when the supermassive black hole was fed with gas to grow. The same processes to build up central regions are also at play in other galaxies. We investigate these processes to get a better understanding of the evolution of galaxies and supermassive black holes. But understanding the formation histories in other Milky-Way-like galaxy centres is even harder, as they are at least 100 times further away than our own Galactic Centre. The goal of this project is to identify different events of gas and star cluster infall that happened in the past. I will analyse observations of the Galactic Centre, obtained with the 8m Gemini South Telescope in Chile. I will measure the velocities and metallicities of thousands of stars and compare the measured data with models of the Galactic Centre. To create these models, I will use the dynamical modelling code DYNAMITE, which is being developed at the University of Vienna. I will constrain which model best describes the observed data. Stars that formed together from the same gas, at the same time, and at the same location, share several properties with each other. By using the information on their velocities, metallicities, and locations, and comparing them to models, we will get the most detailed insights into how, and where the different groups of stars formed, and how they came to be a part of the Galactic Centre.