Magnetic field evolution in interacting galaxies
  Violent gravitational interactions can change the morphologies of galaxies
and, by means of merging, transform them into elliptical galaxies. We aim to
investigate how they affect the evolution of galactic magnetic fields. We
selected 16 systems of interacting galaxies and compared their radio emission
and estimated magnetic field strengths with their star-forming activity,
far-infrared emission, and the stage of tidal interaction. We find a general
evolution of magnetic fields: for weak interactions the strength of magnetic
field is almost constant (10-15muG) as interaction advances, then it increases
up to 2x, peaks at the nuclear coalescence (25muG), and decreases again, down
to 5-6muG, for the post-merger remnants. The magnetic field strength for whole
galaxies is weakly affected by the star formation rate (SFR), while the
dependence is higher for galactic centres. We show that the morphological
distortions visible in the radio total and polarized emission do not depend
statistically on the global or local SFRs, while they do increase with the
advance of interaction. The constructed radio-far-infrared relations for
interacting and non-interacting galaxies display a similar balance between the
generation of cosmic rays, magnetic fields, and the production of the thermal
energy and dust radiation. The process of strong gravitational interactions can
efficiently magnetize the merger's surroundings, having a similar magnetizing
effect on intergalactic medium as supernova explosions or galactic winds. If
interacting galaxies generate some ultra-high energy cosmic rays (UHECRs), the
disk or magnetized outflows can deflect them (up to 23 degrees), and make an
association of the observed UHECRs with the sites of their origin very
uncertain.
