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I am professor for theoretical astrophysics at Heidelberg University. My research activities focus on the formation of stars at present days and in the early universe, on the dynamics of the interstellar medium, on astrophysical turbulence, and on the development of numerical methods for computational astrophysics.

For an overview of my curriculum vitae follow this LINK.

For my website at the Center for Astronomy at Heidelberg University follow this LINK.

I recently received an ERC synergy grant together with Patrick Hennebelle (CEA, Saclay), Sergio Molinari (INAF, Rome), and Leonardo Testi (ESO, Garching). More information is found on this LINK.

Current Research Highlight

May 2020: Formation sites of Population III star formation: The effects of different levels of rotation and turbulence on the fragmentation behaviour of primordial gas

Wollenberg, Katharina M. J., Glover, Simon C. O., Clark, Paul C., Klessen, Ralf S., MNRAS, 494, 1871-1893 (2020) [ADS link]

Fragmentation of the accretion disk in Population III star formation.
Fragmentation of the accretion disk in Population III star formation.

We use the moving-mesh code Arepo to investigate the effects of different levels of rotation and turbulence on the fragmentation of primordial gas and the formation of Population III stars. We consider nine different combinations of turbulence and rotation and carry out five different realizations of each setup, yielding one of the largest sets of simulations of Population III star formation ever performed. We find that fragmentation in Population III star-forming systems is a highly chaotic process and show that the outcomes of individual realizations of the same initial conditions often vary significantly. However, some general trends are apparent. Increasing the turbulent energy promotes fragmentation, while increasing the rotational energy inhibits fragmentation. Within the ~1000 yr period that we simulate, runs including turbulence yield flat protostellar mass functions while purely rotational runs show a more top-heavy distribution. The masses of the individual protostars are distributed over a wide range from a few 10-3 M to several tens of M. The total mass growth rate of the stellar systems remains high throughout the simulations and depends only weakly on the degree of rotation and turbulence. Mergers between protostars are common, but predictions of the merger fraction are highly sensitive to the criterion used to decide whether two protostars should merge. Previous studies of Population III star formation have often considered only one realization per set of initial conditions. However, our results demonstrate that robust trends can only be reliably identified by considering averages over a larger sample of runs.

Earlier Research Highlights

For the all monthly research highlights follow this LINK.

Funding Sources