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Delaying the formation of the first stars The impact of streaming velocities and Lyman-Werner radiation in cosmological hydrodynamical simulations

Schauer, Anna Therese Phoebe

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Abstract

In this thesis, we study which effects can delay the formation of the first stars in the Universe. These Population III stars were the first luminous objects emerging after recombination, starting to end the dark ages. They form in minihaloes or first galaxies, and the minimum mass of these objects is strongly related to the number of Population III stars that formed. In some regions of the Universe, there is an offset velocity between baryons and dark matter, the so-called streaming velocity. In this thesis, we show that in regions with large streaming velocities, the halo masses necessary to form the first stars increase. These regions are the perfect environment for the formation of direct collapse black holes. Feedback in the form of Lyman-Werner radiation emitted by the first stars can destroy molecular hydrogen and prevent the primordial gas cloud from cooling and collapsing. This also leads to an offset in time and halo mass for Population III star formation. To account for the strength of the Lyman-Werner background, we performed simulations that study the escape fraction from minihaloes and the first galaxies. With these results, we provide a piece of the jigsaw of the star formation history of the Universe.

Item Type: Dissertation
Supervisor: Klessen, Prof. Dr. Ralf
Date of thesis defense: 25 October 2017
Date Deposited: 19 Dec 2017 14:47
Date: 2017
Faculties / Institutes: The Faculty of Physics and Astronomy > Dekanat der Fakultät für Physik und Astronomie
Subjects: 520 Astronomy and allied sciences
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