S315p.257 — Magnetic fields and the survival of infalling gas

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Aug 4th at 6:00 PM until 6:00 PM

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Author(s): Alex S Hill1

Institution(s): 1. Haverford College

The short depletion time in galaxies over redshifts ~0-2 suggests that some form of inflow is required to sustain the observed star formation rates. The cosmic star formation rate is thus likely to be approximately the infall rate. However, the physical mechanism by which infalling gas travels from the galaxy's virial radius to the midplane is unclear, since numerical work generally indicates that infalling gas traveling through galactic halos should be disrupted by Kelvin-Helmholtz instabilities and feedback from massive stars before it reaches the disk. Some High velocity clouds (HVCs) around the Milky Way trace this infall. I will present measurements of a >~ 6 microgauss magnetic field in the Smith Cloud HVC, strong enough to stabilize the cloud against disruption. I will also present magnetohydrodynamic simulations of infalling clouds interacting with the ISM in the halo and entering a star-forming disk driven by feedback from massive stars. These simulations will allow numerical tests of the ability of infalling magnetized gas to condense and join the disk.

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