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Magnetic field evolution
in perturbed spiral galaxies
3D modeling
M. Soida, K. Otmianowska- Mazur
Astronomical Observatory of the Jagiellonian University, Kraków
B. Vollmer
Strasbourg Observatory
3D N-body sticky- particle code:
particles = gas cloud complexes or/and star complexes
evolution in an analytically given gravitational potential or with the gravitational
interaction between star complexes
selfgravitation of clouds (tree- code)
inelastic collisions between the clouds: fragmentation, mass exchange,
coalescence
adaptive timestep integrator (Burlisch- Stoer)
ram pressure as an additional external acceleration
= 5.8 10 9
10 000 cloud complexes,
Mtot
49 125 star complexes,
Mhalo = 1.5 10 11
Mbulge = 5.2 10 9
Mdisk = 2.6 10 10
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Gas clouds velocity field evolution:
3D MHD code:
ZEUS 3D
cartesian coordinates, 171 x 171 x 71 cells
grid size 34 kpc x 34 kpc x 20 kpc
induction (dynamo) equation
Magnetic field evolution:
outflow boundary conditions
Integation code:
B-cube orientation (line of sight orientation)
integration of synchrotron emissivity along the line of sight
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Polarization intensity maps:
convolution with Gaussian beam
Observations:
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Magnetic fields follow well the peculiar gas flows caused by interactions either with neighbouring objects or with the
intergalactic medium.
Gas flows induced by interactions may constitute an important field amplification mechanism. Galaxies seldom live
alone: the "interactional" field amplification mechanism may be a clue to magnetic field evolution.
The radio polatrization observations provide a very good tracer of gas dynamics of interacting objects in the sky plane.
This adds two dimensions to only one provided by the radial velocity studies.
In this experiment only the regular magnetic field component is calculated - only the polarized intensity maps are
available
No back- reaction of the magnetic field on the gas kinematics is taken into account