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| EPoS Contribution |
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The Origin of Filamentary Star Forming Clouds in Magnetised Galaxies
Bastian Koertgen HS, Hamburg, DE | |
| Observations show that galaxies and their interstellar media are pervaded by strong magnetic fields with energies in the diffuse component being at least comparable to the thermal and even as large or larger than the turbulent energy. It is well known that these strong magnetic fields prevent the gas from fragmenting into stars. So how do star forming molecular clouds arise in highly magnetised galaxies? By using global numerical simulations of strongly magnetised and self-gravitating galactic discs, we here show that the buoyancy of the magnetic field (the Parker instability) leads to the formation of giant filamentary regions. These are no longer magnetically dominated, become gravitationally unstable and fragment into molecular clouds. Our results thus provide a solution to the long-standing problem of how to form stars out of a magnetically dominated medium and address recent Planck observations on the relationship between filaments and magnetic fields in the Milky Way. | |
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| Caption: Iso-surface maps of the density (n = 10 cm-3 in red) and magnetic field lines (black lines) within the disc of the simulation with initial plasma-beta = 0.25. When the magnetic field becomes Parker unstable, the gas motion is affected, which results in the formation of spurs. Shear disturbs them locally. The filaments are prone to gravitational instability and subsequently fragment into individual objects. At this time, t = 300 Myr, these fragments are still well connected via the magnetic field lines. In the fully fragmented stage, t = 400 Myr, cloud-cloud interactions change the number of fragments and locally tangle the magnetic field. | |
| Collaborators: R. Banerjee, HS, DE R.E. Pudritz, DPA, CA W. Schmidt, HS, DE |
Suggested Session:
Magnetic fields |