Magnetic fields in barred galaxies
A fully three-dimensional (3D) MHD model is applied to simulate the evolution
of large-scale magnetic field in a barred galaxy possessing a gaseous halo
extended to about 3 kpc above the galactic plane. As the model input we
use a time dependent velocity field of molecular gas resulting from
self-consistent 3D N-body simulations of the galactic disk.
We assume that the gaseous halo rotates differentially co-rotating with the
disk (Kalberla & Kerp, 1998 and references therein) or decreasing its velocity
in the Z direction. A dynamo process included in the model yields the
amplification of the magnetic field as well as the formation of field
structures high above the galactic disk. The simulated magnetic fields are used
to construct the models of high-frequency (Faraday rotation-free) polarized
radio emission accounted for effects of projection and limited resolution, thus
suitable for direct comparisons with observations.
We found that the resultant magnetic field correctly reproduces the observed
structures of polarization B-vectors, forming coherent patterns, well aligned
with spiral arms and with the bar. The magnetic arms located in the interarm
regions are also observed. The inclusion of the galactic halo constitutes a
step toward the realistic model of galactic magnetic fields including as many
as possible dynamical components.
References
- Otmianowska-Mazur K., Elstner D., Soida M., Urbanik M., 2002, "Magnetic fields and radio polarization of barred galaxies. 3D dynamo simulations", AA 384, 48
- Otmianowska-Mazur K., Vollmer B., 2003, "Magnetic field evolution in galaxies interacting with the intracluster medium. 3D numerical simulations", AA 402, 879