Magnetic field amplification and star bursts induced by mergers of disk galaxies

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We plan to explore the evolution of the magnetic field, the star formation activity, and the molecular gas during mergers of disk galaxies by means of numerical simulations. Both theoretical and observational studies showed that mergers play a significant role in the evolution of galaxies and there are indications of magnetic field amplification during mergers. Based on preliminary numerical simulations of adiabatic gaseous disks without dark matter halos, we propose a substantially more realistic model of galaxy mergers by introducing dark-matter halos modelled be particles, a more detailed treatment of chemical reactions, particularly the formation of molecular hydrogen, and subgrid physics encompassing turbulence, star formation, and feedback. We will employ the magnetohydrodynamical adaptive mesh refinement code Enzo, including a novel subgrid-scale model for magnetohydrodynamical turbulence and the astrochemistry package KROME to model the formation of molecular gas in greater detail than in previous galaxy simulations. Moreover, we will apply a dynamical model of star formation that is not based on a fixed efficiency parameter corresponding to the observed Kennicutt-Schmidt relation for isolated galaxies. This approach was successfully applied in simulations of isolated disk galaxies without magnetic fields, for which the correct efficiency is reproduced by the model. In this project, we will extend the model to the magnetohydrodynamical case, test it in isolated disk simulations and then apply it to mergers. The outlined methodology will allow us to unravel the impact of different channels of turbulence production on magnetic field amplification (basically instabilities vs feedback), the dependence on merger parameters such as disk orientation and impact parameter, and the relation between star formation and molecular gas content in merging systems.