Rotation measure and synchrotron emission signatures in simulations of
  magnetized galactic discs
  We analyse observational signatures of magnetic fields for simulations of a
Milky-Way like disc with supernova-driven interstellar turbulence and
self-consistent chemical processes. In particular, we post-process two
simulations data sets of the SILCC Project for two initial amplitudes of the
magnetic field, $B_0 = $ 3 and 6 $\mu$G, to study the evolution of Faraday
rotation measures (RM) and synchrotron luminosity. For calculating the RM,
three different models of the electron density $n_e$ are considered. A constant
electron density, and two estimations based on the density of ionized species
and the fraction of the total gas, respectively. Our results show that the RM
profiles are extremely sensitive to the $n_e$ models, which assesses the
importance of accurate electron distribution observations/estimations for the
magnetic fields to be probed using Faraday RMs. As a second observable of the
magnetic field, we estimate the synchrotron luminosity in the simulations using
a semi-analytical cosmic ray model. We find that the synchrotron luminosity
decreases over time, which is connected to the decay of magnetic energy in the
simulations. The ratios between the magnetic, the cosmic ray, and the thermal
energy density indicate that the assumption of equipartition does not hold for
most regions of the ISM. In particular, for the ratio of the cosmic ray to the
magnetic energy the assumption of equipatition could lead to a wrong
interpretation of the observed synchrotron emission.
