Galactic structure (of the Milky Way and in the Near Universe)
PhD Projects
Kinematically-selected halo stars
Sean Ryan, Phil Lucas, David Pinfield
The project will make use of newly acquired proper motion data for stars in the UKIDSS and VISTA surveys, and other photometric surveys, to identify a sample of halo dwarfs. The stars will be used for a range of further follow-up studies including (1) the identification of a larger sample of halo stars which are crucial for finding extremely metal-poor stars, (2) assessing the fraction of halo dwarfs which are carbon rich (in contrast to current statistics based on spectroscopic selection of giants), (3) to seek further evidence of the existence of Galactic bulge stars in the solar neighbourhood and then to characterise them, (4) to identify common proper motion pairs which belong to the halo and to use them to study mass-dependences in halo star evolution such as lithium depletion, and (5) to do other opportunistic things.
Improving models of massive stars
Thomas Rauscher, R. Hirschi (Keele), Sean Ryan
Understanding the origin of the elements and the production of nuclides throughout the Galactic history in various astrophysical sites is one of the most exciting questions in physics. It requires interdisciplinary research combining the fields of astrophysics, astronomy, nuclear and particle physics. In this context we are offering a PhD project with emphasis on astrophysical modelling of hydrostatic and explosive phases of stellar evolution. The student will work with state-of-the-art stellar models, trying to improve spherically symmetric simulations through new insights gained from 3-D hydrodynamics, and study the effects on nucleosynthesis. Comparison to observational data further constrains the models. At the same time, variations in the patterns of produced nuclei stemming from uncertainties in the nuclear input will be explored. An estimate of general uncertainties in the rates of reactions as employed in astrophysical simulations will be derived and applied in computation-heavy Monte Carlo variation studies to systematically quantify, for the first time, the main sensitivities of massive star nucleosynthesis. The results will allow to prioritize further improvements in the astrophysical and nuclear models in close collaboration with international groups. Depending on the project progress, the student will also be directly involved in this extension.
Astrophysical reaction rates for heavy element nucleosynthesis
Thomas Rauscher, Chiaki Kobayashi, C. Fröhlich (NCSU, USA)
Understanding the origin of the elements and the production of nuclides throughout the Galactic history in various astrophysical sites is among the most exciting questions in physics. In this context we are offering a project with emphasis on modelling nuclear reactions in stellar and explosive environments. Astrophysical reaction rates are key quantities to understand nucleosynthesis. Nuclear reactions proceed differently in astrophysical plasmas than in the laboratory and additional effects have to be considered. The majority of isotopes created in explosive nucleosynthesis is very short-lived and cannot be studied experimentally at all. Model predictions of nuclear reactions are therefore essential. The project involves the implementation of previously unconsidered effects and improved knowledge of nuclear properties into existing reaction models, and to test the new predictions in comparison with the scarce experimental data. The impact of the results on production of nuclei in various astrophysical environments - stars, supernovae, explosive nuclear burning on the surface of a neutron star - will be studied in post-processing reaction networks. In order to obtain a larger picture of the global impact, this will be tied to Galactic Chemical Evolution models to investigate their sensitivity to uncertainties in the knowledge of fundamental nuclear properties.