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| Paper: |
Magnetohydrodynamic Simulations of Barred Galaxies |
| Volume: |
474, Numerical Modeling of Space Plasma Flows (ASTRONUM2012) |
| Page: |
78 |
| Authors: |
Kim, W.-T. |
| Abstract: |
Magnetic fields are pervasive in barred galaxies, especially in
gaseous substructures such as dust lanes and nuclear rings. To
explore the effects of magnetic fields on the formation of the
substructures as well as on the mass inflow rates to the galaxy
center, we run two-dimensional, ideal magnetohydrodynamic
simulations. We use a modified version of the Athena code
whose numerical magnetic diffusivity is shown to be of third order
in space. In the bar regions, magnetic fields are compressed
and abruptly bent around the dust-lane shocks. The associated
magnetic stress not only reduces the peak density of the dust-lane shocks
but also removes angular momentum further from the gas that is moving
radially in. Nuclear rings that form at the location of centrifugal
barrier rather than resonance with the bar are smaller and more
radially distributed, and the mass flow rate to the galaxy center
is correspondingly larger in models with stronger magnetic fields.
Outside the bar regions, the bar potential and strong shear conspire
to amplify the field strength near the corotation resonance. The
amplified fields transport angular momentum outward, producing
trailing magnetic arms with strong fields and low density. The base
of the magnetic arms are found to be unstable to a tearing-mode
instability of magnetic reconnection. This produces numerous
magnetic islands that eventually make the outer regions highly
chaotic. |
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