The Formation of Kiloparsec-Scale HI Holes in Dwarf Galaxies
  The origin of kpc-scale holes in the atomic hydrogen (H I) distributions of
some nearby dwarf irregular galaxies presents an intriguing problem. Star
formation histories (SFHs) derived from resolved stars give us the unique
opportunity to study past star forming events that may have helped shape the
currently visible H I distribution. Our sample of five nearby dwarf irregular
galaxies spans over an order of magnitude in both total H I mass and absolute
B-band magnitude and is at the low mass end of previously studied systems. We
use Very Large Array H I line data to estimate the energy required to create
the centrally dominant hole in each galaxy. We compare this energy estimate to
the past energy released by the underlying stellar populations computed from
SFHs derived from data taken with the Hubble Space Telescope. The inferred
integrated stellar energy released within the characteristic ages exceeds our
energy estimates for creating the holes in all cases, assuming expected
efficiencies. Therefore, it appears that stellar feedback provides sufficient
energy to produce the observed holes. However, we find no obvious signature of
single star forming events responsible for the observed structures when
comparing the global SFHs of each galaxy in our sample to each other or to
those of dwarf irregular galaxies reported in the literature. We also fail to
find evidence of a central star cluster in FUV or Halpha imaging. We conclude
that large H I holes are likely formed from multiple generations of star
formation and only under suitable interstellar medium conditions.
