Magnetic fields during galaxy mergers
  Galaxy mergers are expected to play a central role for the evolution of
galaxies, and may have a strong impact on their magnetic fields. We present the
first grid-based 3D magneto-hydrodynamical simulations investigating the
evolution of magnetic fields during merger events. For this purpose, we employ
a simplified model considering the merger event of magnetized gaseous disks in
the absence of stellar feedback and without a stellar or dark matter component.
We show that our model naturally leads to the production of two peaks in the
evolution of the average magnetic field strength within 5 kpc, within 25 kpc
and on scales in between 5 and 25 kpc. The latter is consistent with the peak
in the magnetic field strength reported by Drzazga et al. (2011) in a merger
sequence of observed galaxies. We show that the peak on the galactic scale and
in the outer regions is likely due to geometrical effects, as the core of one
galaxy enters the outskirts of the other one. In addition, there is a physical
enhancement of the magnetic field within the central ~5 kpc, reflecting the
enhancement in density due to efficient angular momentum transport. We conclude
that high-resolution observations of the central regions will be particularly
relevant to probe the evolution of magnetic field structures during merger
events.
