title: Diversity of Population III Star Formation : influence of rotation, turbulence, and magnetic fields on the fragmentation behavior of Population III protostellar disks and implications for the later evolution of the star-forming environment
creator: Wollenberg, Katharina Margaretha Johanna
subject: ddc-500
subject: 500 Natural sciences and mathematics
subject: ddc-520
subject: 520 Astronomy and allied sciences
subject: ddc-530
subject: 530 Physics
description: The aim of this thesis is to improve our understanding of the fragmentation behavior of Population III protostellar disks under the influence of rotation, turbulence, and magnetic fields. We further evaluate consequences that may be inferred for the later evolution of the star-forming halo and its surroundings with respect to protostellar ejections and in terms of the impact of radiative feedback on later chemical enrichment of neighboring halos.  In the main part of this thesis, we follow the collapse of a primordial gas cloud until the formation of the first protostar and the creation of a highly gravitationally unstable protostellar disk system. We find that turbulence promotes the fragmentation of the protostellar disk and both rotation and magnetic fields can provide some stabilization against it. While the total mass growth of the collection of protostars is only mildly affected by rotation and turbulence, magnetic fields can have such a strong impact on the dynamical evolution of the disk system that accretion onto the protostars is highly disturbed and their mass growth is significantly reduced. In spite of all the differences, the disk generally breaks up into a protostellar cluster that develops a top-heavy mass function. Interactions between protostars in the cluster are highly dynamical and lead to a considerable number of protostellar ejections. We demonstrate that some of these ejected Population III protostars, even if they continue to accrete for some longer period after they have left the disk environment, continue to have masses of M < 0.8 solar mass. Hence, they have lifetimes longer than the current age of the Universe and thus describe Population III candidates that could still be observable today.  In another project, we assess the role of photoevaporation of a pristine halo by a near-by Population III star prior to the supernova explosion of that star. We demonstrate that it is crucial for realistic simulations of metal enrichment to account for the photoevaporation as the radiation ablates and thins out the outer halo layers and thus makes the halo more susceptible to mixing with the metals from the supernova ejecta.  In this thesis, we use both analytical estimations and numerical simulations. Further tests are conducted to investigate the performance of our numerical methods and the sensitivity of our results to the numerical resolution. We demonstrate that general trends, in particular when effects of turbulence are examined, cannot be reliably deduced from only a single numerical run. Instead a statistical analysis of an ensemble of realizations based on the same initial conditions needs to be considered.
date: 2019
type: Dissertation
type: info:eu-repo/semantics/doctoralThesis
type: NonPeerReviewed
format: application/pdf
identifier: https://archiv.ub.uni-heidelberg.de/volltextserverhttps://archiv.ub.uni-heidelberg.de/volltextserver/26028/1/WollenbergKMJ_thesis.pdf
format: application/pdf
identifier: https://archiv.ub.uni-heidelberg.de/volltextserverhttps://archiv.ub.uni-heidelberg.de/volltextserver/26028/7/corrigendum.pdf
identifier: DOI:10.11588/heidok.00026028
identifier: urn:nbn:de:bsz:16-heidok-260280
identifier:   Wollenberg, Katharina Margaretha Johanna  (2019) Diversity of Population III Star Formation : influence of rotation, turbulence, and magnetic fields on the fragmentation behavior of Population III protostellar disks and implications for the later evolution of the star-forming environment.  [Dissertation]     
relation: https://archiv.ub.uni-heidelberg.de/volltextserver/26028/
rights: info:eu-repo/semantics/openAccess
rights: http://archiv.ub.uni-heidelberg.de/volltextserver/help/license_urhg.html
language: eng