Cosmic Rays: The Key to Galaxy Formation?

HITS Astrophysicist Christoph Pfrommer starts with new Junior Research group “High Energy Astrophysics and Cosmology” – funded by a €2 million ERC Consolidator Grant.

The new Junior Research Group “High Energy Astrophysics and Cosmology” (HAC) has now started at the Heidelberg Institute for Theoretical Studies (HITS). HITS astrophysicist Dr. Christoph Pfrommer has been awarded a Consolidator Grant of the European Research Council (ERC). He will use the €2 million research grant to establish his own group. At present there are 13 research groups – including Pfrommer’s group – working at HITS on data-driven science, from mathematics to molecular biology. With four groups, astrophysics and astronomy represents one of the key areas of the institute.

“The addition of this new group shows how remarkably quickly HITS has established itself as a research institute over the last six years,” Scientific Director Rebecca Wade says. “A total of four HITS scientists currently hold an ERC grant.”

Understanding the physics of galaxy formation is arguably among the greatest problems in modern astrophysics. Christoph Pfrommer investigates the impact of cosmic rays on galaxy and cluster formation. Cosmic rays originate in supernova explosions and produce galactic winds that, among other things, influence star formation. These gigantic gaseous outflows in galaxies are generated by similar mechanisms to those that cause solar flares and coronal mass ejections and thus are responsible for geomagnetic storms on Earth. In contrast to these stormy space weather events, the gigantic galactic winds are harmless for us humans. “But they seem to represent an essential phase in the early, violent period of galaxy formation”, says Pfrommer. The cosmological computer simulation Illustris has shown that these outflows are not only necessary to form realistic spiral galaxies, but also appear to be crucial in explaining the observed diversity of galaxy morphologies, i.e., their appearance in form of spirals and ellipticals. While current computer simulations are modelling these gaseous outflows phenomenologically, Pfrommer’s group aims at modelling the underlying physics of cosmic rays, magnetic fields, and plasma waves in great detail. To investigate the cosmic-ray propagation in galactic magnetic fields, the researchers will employ and expand the AREPO code that has been developed at HITS. In order to be able to conduct the next generation of simulations, the HITS computer cluster is in the process of being upgraded. The simulation results will be validated by taking advantage of new observational capabilities at radio to gamma-ray wavelengths.

One of the central research questions of the new group is whether the strong galactic winds are indeed caused by cosmic rays or whether there is another – yet unknown – mechanism at work. “Perhaps it will turn out that the currently favoured cold dark matter model is not complete and has to be modified”, explains Pfrommer, “for instance, by taking into account self-interactions of dark matter. In any case, I expect this to be an exciting journey, with hopefully many surprises and new discoveries.”

Pfrommer studied Physics in Jena (Germany), Harvard (USA) and at the Max Planck Institute for Astrophysics in Garching (Germany). After his Ph.D. at the Ludwig-Maximilians-Universität in Munich, he worked as a postdoctoral and senior research associate at the Canadian Institute for Theoretical Astrophysics (CITA) in Toronto. In summer 2010, he joined the “Theoretical Astrophysics” group at HITS (led by Prof. Volker Springel) as a senior researcher. In January 2014, Christoph Pfrommer was the first active HITS employee to obtain a habilitation at Heidelberg University.
With his research project CRAGSMAN – The Impact of Cosmic Rays on Galaxy and Cluster Formation – Christoph Pfrommer became the third scientist at HITS to be awarded an ERC grant, joining astrophysicist Volker Springel (ERC Starting Grant) and mathematician Tilmann Gneiting (ERC Advanced Grant). In summer 2015, mathematician Anna Wienhard (Heidelberg University), who also holds an ERC Consolidator Grant, joined HITS as head of the associated group “Groups and Geometry”, bringing the number of ERC grant awardees at HITS to four.

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Heidelberg Institute for Theoretical Studies (HITS)
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