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| Paper: |
Kiloparsec-Scale Simulations of Magnetised Molecular Clouds in Disk Galaxies |
| Volume: |
474, Numerical Modeling of Space Plasma Flows (ASTRONUM2012) |
| Page: |
122 |
| Authors: |
Van Loo, S.; Butler, M. J.; Tan, J. C.; Falle, S. A. E. G. |
| Abstract: |
We present simulations of the evolution of self-gravitating dense gas
on kiloparsec-size scales in a galactic disk, designed
to study dense clump formation from giant molecular clouds (GMCs). These dense clumps
are expected to be the precursors to star clusters and this process may be the rate
limiting step controlling star formation rates in galactic systems as described by
the Kennicutt–Schmidt relation.
The evolution of these simulated GMCs and clumps is determined by self-gravity balanced
by turbulent pressure support and the large scale galactic shear.
While the cloud structures and densities significantly change during their evolution, they
remain roughly in virial equilibrium for time scales exceeding
the free-fall time of GMCs, indicating that energy from the galactic shear
continuously cascades down. We implement star formation at a slow,
inefficient rate of 2% per local free-fall time, but this still yields global star
formation rates that are ∼ two orders of magnitude larger than the observed
Kennicutt–Schmidt relation due to the over-production of dense clump gas.
To explain this discrepancy, we anticipate magnetic fields to provide additional
support. Low-resolution simulations indeed show that the magnetic field
reduces the star formation rate. |
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