Extragalactic Astrophysics:
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Project leader: Sabine Schindler
Institute of Astro and Particle Physics
Structure formation in the universe can be studied by simulating the evolution of galaxies and galaxy clusters. In particular the influence of the interaction of galaxies with their surroundings on the evolution is still highly debated. In all simulations various components of galaxies and clusters (including gas and dark matter) have to be taken into account and treated with different numerical techniques. An important aspect is always the comparison with observations to ensure that the calculated models are realistic. In this context we offer the following two thesis topics:
- Simulations of the enrichment of the intra-cluster medium with different elements
- Simulations of the interaction of a galaxy with the intra-cluster medium
A galaxy moving through an intra-cluster medium. From left to right more and more gas is bing stripped from the object.
Extragalactic Astrophysics:
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Using the modular code of galaxy cluster simulations (combined N-body / hydrodynamics) with various enrichment processes, which we have developed over the last years, in this project the cluster evolution including element yields of supernova II and Ia explosions and possibly other mechanisms will be calculated. For various enrichment processes (ram-pressure stripping, galactic winds, galaxy interactions) the intra-cluster medium pollution with different elements (Fe, Si, O, Ar, Ni…) will be followed. Also, optimising the code with respect to parallelised / distributed computing is a part of this project. The spatial distribution and time evolution of elements and element ratios, depending on the formation history of the cluster will be determined. Furthermore, the results of these simulations will be compared with observations by calculating projected metallicity maps exactly as they would be observed by an X-ray telescope. For this comparison various statistical measures will have to be tested, which take into account the different resolutions, sensitivities and errors. Also, a quantitative measure that is applicable both to simulated and observational data will be developed. This measure shall be able to compare quantitatively simulated and observed metallicity maps and hence it shall be able to sort out unrealistic simulated maps. In an iterative procedure the enrichment processes and element yields will be improved until realistic maps are obtained. In this way constraints can be put on the efficiency of enrichment processes and on the contribution of different supernova types to the metal abundance on large scales. Finally, an extension of the current code, which only takes into account the thermal intra-cluster gas, to high-energy non-thermal components in clusters will be investigated.
Extragalactic Astrophysics:
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In recent simulations we found star formation in the wake of a galaxy that is in the process of being stripped by the intra-cluster medium, which is a highly ionised plasma. Some of the stars formed there are not bound to the galaxy, but form part of the intra-cluster stellar population, so that this process is able to produce stars between the galaxies. So far it was only possible to obtain a qualitative result. We know that this process is taking place, but we do not know yet how efficient it is, i.e. what percentage of unbound stars it produces. For this determination several improvements of the code are necessary, which have to be implemented in the course of this project. An example of these is a better treatment of turbulence, which can influence the amount of stripped gas considerably.
With the improved code star formation in galaxy wakes will be studied quantitatively depending on galaxy and intra-cluster medium properties. Special emphasis will be put on the observability of newly formed stars and its comparison with observations from ESO telescopes. Furthermore, the observational limits of different star formation indicators at different wavelengths for current and future telescopes will be calculated.