The following projects are available, unless stated otherwise. The projects take one year to complete and should finish with a submitted research paper. The student will work under supervision by Pavel Kroupa and in collaboration with PhD students and post-doctoral researchers working on related areas at the Sternwarte, and will be embedded in international research initiatives.
The Galaxy has about a dozen satellites which may or may not be dark-matter dominated. Clarification of this issue is of very high relevance for modern cosmological theory. This project deals with simple aspects of the dynamical evolution of the Milky Way satellites.
Stars evaporate from a satellite galaxy or halo globular cluster forming thin, kinematically cold streams. These have been detected by observation. Interactions of these cold streams with a clumpy dark-matter halo of the Milky Way, which modern cosmological theory considers to be a necessity, broadens these streams, sothat their life-times as cold features is limited. This project investigates the heating of the streams for various models of the dark matter halo, and is therefore of much significance for constraining the type of particles which dark matter can be composed of.
The disks of galaxies typically have a thin component with a scale height of about 250 pc and a thick component with a scale height of about 1 kpc. Various formation scenarious for the thick disk exist, one of them being the accretion of cosmological sub-structures. This project deals with the various disk-heating scenarious in order to improve the understanding of classical heating mechanisms. The results will constrain the properties of the Milky Way halo sub-structures.
Observations of the distribution of star-cluster masses around many galaxies suggest that the cluster-mass function for old clusters is a log-normal with a mean mass near 10^5 Msun. However, the mass function of very young clusters found in interacting galaxies has been found to be a power-law down to the least massive clusters detected. This project deals with this discrepancy, whereby tidal disruption of clusters is merely one physical mechanism that destroys low-mass clusters.
Star clusters form from a molecular cloud core with low efficiency. That is, most of the gas is expelled from the cluster region by the feedback of the young stars. The physical details remain unknown, but the general effect is to unbind the cluster of young stars. Using state-of-the art stellar-dynamical tools this project will quantify the fraction of stars that re-virialise to form a surviving star cluster as a function of a number of key physical parameters.
The distribution of stellar masses is one of the most fundamental astrophysical distribution functions. Research on the stellar initial mass function (IMF) touches areas ranging from star-formation, the profusion of free-floating planetary mass objects, brown dwarfs, through to the stellar-dynamical evolution of star clusters and the dynamical and chemical evolution of galaxies. This project will develop an iterative method to extract the stellar mass function given an observed distribution of stellar luminosities.