Can the cosmic-ray driven dynamo model explain the observations of the polarized emission of edge-on galaxies?

Abstract

In the present paper we construct maps of polarized synchrotron radio emission of a whole galaxy, based on local models of the cosmic ray (CR) driven dynamo. We perform numerical simulations of the dynamo in local Cartesian domains, with shear-periodic boundary conditions, placed at the different galactocentric radii. Those local solutions are concatenated together to construct the synchrotron images of the whole galaxy. The main aim of the paper is to compare the model results with the observed radio continuum emission from nearly edge-on spiral galaxy. On the basis of the modeled evolution of the magnetic field structure, the polarization maps can be calculated at different time-steps and at any orientation of the modeled galaxy. For the first time a self-consistent cosmic-ray electron distribution is used to integrate synchrotron emissivity along the line of sight. Finally, our maps are convolved with the given radiotelescope beam. We show that it is possible to reconstruct the extended magnetic halo structures of the edge-on galaxies (so called X-shaped structures).