Constraining the Magnetic Field of the Smith High Velocity Cloud using
  Faraday rotation
  The Smith Cloud is a high velocity cloud (HVC) with an orbit suggesting it
has made at least one passage through the Milky Way disk. A magnetic field
found around this cloud has been thought to provide extra stability as it
passes through the Galactic halo. We use the Karl G. Jansky Very Large Array to
measure Faraday rotation measures (RMs) towards 1105 extragalactic background
point sources behind and next to the Smith Cloud to constrain the detailed
geometry and strength of its magnetic field. The RM pattern across the cloud
gives a detailed morphology of the magnetic field structure which indicates a
field draped over the ionized gas and compressed at the head of the cloud. We
constrain the peak line-of-sight magnetic field strength to > +5 uG and create
a model of the magnetic field to demonstrate that a draped configuration can
qualitatively explain the morphology of the observed RMs.
