Magnetized Gas Clouds can Survive Acceleration by a Hot Wind
  We present three-dimensional magnetohydrodynamic simulations of magnetized
gas clouds accelerated by hot winds. We initialize gas clouds with tangled
internal magnetic fields and show that this field suppresses the disruption of
the cloud: rather than mixing into the hot wind as found in hydrodynamic
simulations, cloud fragments end up co-moving and in pressure equilibrium with
their surroundings. We also show that a magnetic field in the hot wind enhances
the drag force on the cloud by a factor ~(1+v_A^2/v_wind^2)$, where v_A is the
Alfven speed in the wind and v_wind measures the relative speed between the
cloud and the wind. We apply this result to gas clouds in several astrophysical
contexts, including galaxy clusters, galactic winds, the Galactic center, and
the outskirts of the Galactic halo. Our results can explain the prevalence of
cool gas in galactic winds and galactic halos and how such cool gas survives in
spite of its interaction with hot wind/halo gas. We also predict that drag
forces can lead to a deviation from Keplerian orbits for the G2 cloud in the
galactic center.
