Supernovae and photoionizing feedback in spiral arm molecular clouds
  We explore the interplay between supernovae and the ionizing radiation of
their progenitors in star forming regions. The relative contributions of these
stellar feedback processes are not well understood, particularly on scales
greater than a single star forming cloud. We focus predominantly on how they
affect the interstellar medium. We re-simulate a 500 pc^2 region from previous
work that included photoionization and add supernovae. Over the course of 10
Myr more than 500 supernovae occur in the region. The supernovae remnants cool
very quickly in the absence of earlier photoionization, but form much larger
and more spherical hot bubbles when photoionization is present. Overall, the
photoionization has a significantly greater effect on gas morphology and the
sites of star formation. However, the two processes are comparable when looking
at their effect on velocity dispersion. When combined, the two feedback
processes increase the velocity dispersions by more than the sum of their
parts, particularly on scales above 5 pc.
