Supershells in the Multi-Phase Milky Way: Insights from HI Synthesis
  Imaging and CO Surveys
  We present new parsec-scale resolution data from a multi-phase study of the
ISM in the walls of Galactic supershells. HI synthesis images and CO survey
data reveal a wealth of substructure, including dense-tipped fingers and
extended molecular clouds embedded in shell walls. We briefly consider
formation scenarios for these features, and suggest that both the interaction
of an expanding shell with pre-existing dense clouds, as well as in-situ
formation of CNM and molecular gas, are likely to be relevant. Future work will
also examine the role of instabilities in structure formation and breakup, and
will investigate the presence of high-altitude gas associated with supershells
and chimneys.
