Evolution of Blister-Type HII Regions in a Magnetized Medium
  We use the three-dimensional Athena ionizing radiation-magnetohydrodynamics
(IRMHD) code to simulate blister-type HII regions driven by stars on the edge
of magnetized gas clouds. We compare these to simulations of spherical HII
regions where the star is embedded deep within a cloud, and to non-magnetized
simulations of both types, in order to compare their ability to drive
turbulence and influence star formation. We find that magnetized blister HII
regions can be very efficient at injecting energy into clouds. This is partly a
magnetic effect: the magnetic energy added to a cloud by an HII region is
comparable to or larger than the kinetic energy, and magnetic fields can also
help collimate the ejected gas, increasing its energy yield. As a result of
these effects, a blister HII region expanding into a cloud with a magnetic
field perpendicular to its edge injects twice as much energy by 5 Myr as a
non-magnetized blister HII region driven by a star of the same luminosity.
Blister HII regions are also more efficient at injecting kinetic energy than
spherical HII regions, due to the recoil provided by escaping gas, but not by
as much as predicted by some analytic approximations.
