Monday 15 Oct 2018[Seminar] Magnetised clouds in the Galactic corona: Fuel for future star formation?

Asger Gronnow - University of Sydney

Laver LT3 11:30-12:30

The Galactic halo contains a complex ecosystem of multiphase
intermediate-velocity and high-velocity gas clouds whose origin has
defied clear explanation. They are generally believed to be involved in
a Galaxy-wide recycling process, either through an accretion flow or a
large-scale fountain flow, or both. In this talk I will present my work
on how the magnetic field in the halo affects these processes using
magnetohydrodynamic (MHD) simulations. The magnetic field becomes
'draped' around the clouds as they move through the halo and this field
suppresses hydrodynamic instabilities at the cloud-halo interface. This
has widespread implications for gas accretion. The suppression of
instabilities prolongs the survival of High-Velocity Clouds (HVCs) so
that they are more likely to reach the disk. It also suppresses the
mixing of cloud-halo material in the wakes of clouds ejected by the
Galactic fountain. This leads to less condensation of cold gas that can
be accreted through the fountain process. In addition, the draping of
the magnetic field around clouds means that observational constraints on
magnetic fields around HVCs can be used to roughly infer their
distances. This is useful to constrain their masses and thereby how
important they are as a source of accretion.

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