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On the formation of the Milky Way system in cosmological context - A numerical study

Buck, Tobias

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Abstract

State-of-the-art cosmological hydrodynamical simulations have succeeded in modelling realistic Milky Way (MW) type galaxies with spatial resolution of the order of a few hundred parsec, similar to the scale-height of MW's stellar disc and the half-light radius of classical satellite galaxies. I divide the present study into two parts, the build-up of MW's stellar disc and bulge and the formation and evolution of its satellites and dwarf galaxies.

In the first part I show that observed clumpy stellar discs in the early phases of the formation of the Galaxy are dynamically unimportant for its further evolution. This confirms recent observational results where a non linear mapping between stellar mass and light causes stellar discs to appear clumpy. I turn then to explore the formation mechanism of a peanut bulge in cosmological context. I study the kinematical properties of the central stellar populations of a model galaxy using a kinematical decomposition technique and find that the observed kinematic features of the (MW) bulge can only be explained if it consists of both, a peanut bulge and a spherically symmetric bulge both formed via disc instabilities. Observing and disentangling both components will soon be possible thanks to large scale Galactic surveys like Gaia.

In the second part I study the dwarf galaxy population of (MW) mass galaxies. The simulations presented here are among the first to be able to study the formation of dwarf satellite galaxies in a realistic cosmological environment. The employed sub-grid models of the simulations reconcile simulated and observed Local Group satellite mass functions and produce dwarf galaxies whose central stellar velocity dispersion agrees with observations. Using the dwarf galaxies, I test the observational prospects of identifying tidally affected dwarfs in the Local Group using three observables: their distance, line-of-sight velocity and central velocity dispersion. Finally, I investigate the evolution of planes-of-satellites in the framework of the Cold Dark Matter model with a cosmological constant (ΛCDM). These planes quickly dissolve because they consist of a large fraction of chance aligned satellites as recently confirmed with the proper motions of the classical satellite galaxies derived from Gaia data.

Item Type: Dissertation
Supervisor: Rix, Prof. Dr. Hans-Walter
Date of thesis defense: 19 October 2018
Date Deposited: 14 Nov 2018 05:58
Date: 2018
Faculties / Institutes: The Faculty of Physics and Astronomy > Dekanat der Fakultät für Physik und Astronomie
Subjects: 500 Natural sciences and mathematics
520 Astronomy and allied sciences
530 Physics
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