Simulating magnetic fields in the Antennae galaxies
  We present self-consistent high-resolution simulations of NGC4038/4039 (the
"Antennae galaxies") including star formation, supernova feedback and magnetic
fields performed with the N-body/SPH code Gadget, in which magnetohydrodynamics
are followed with the SPH method. We vary the initial magnetic field in the
progenitor disks from 1 nG to 100 muG. At the time of the best match with the
central region of the Antennae system the magnetic field has been amplified by
compression and shear flows to an equilibrium field of approximately 10 muG,
independent of the initial seed field. These simulations are a proof of the
principle that galaxy mergers are efficient drivers for the cosmic evolution of
magnetic fields. We present a detailed analysis of the magnetic field structure
in the central overlap region. Simulated radio and polarization maps are in
good morphological and quantitative agreement with the observations. In
particular, the two cores with the highest synchrotron intensity and ridges of
regular magnetic fields between the cores and at the root of the southern tidal
arm develop naturally in our simulations. This indicates that the simulations
are capable of realistically following the evolution of the magnetic fields in
a highly non-linear environment. We also discuss the relevance of the
amplification effect for present day magnetic fields in the context of
hierarchical structure formation.
