HI as a Probe of Structure in the Interstellar
Medium of External Galaxies (Review)
M.S. Oey
This review presents a perspective on recent advances in understanding
neutral ISM structure in external galaxies. HI is a
fundamental probe of galactic baryonic material, and its structure and
distribution offer vital signatures of dynamical and evolutionary
processes that drive star formation and galaxy evolution. New,
high-resolution HI data cubes for external
galaxies now reveal the features and topology of the
entire neutral ISM, which here are considered on scales of 10 - 1000
pc. I focus on the two principal candidates for HI structuring,
mechanical feedback from massive stars and turbulence; other
mechanisms are also considered, especially with respect to supergiant
shells. While confirmation for both mechanical feedback and turbulent
processes exists, it remains unclear how these mechanisms yield the
global, steady-state, scale-free HI properties that are observed.
Understanding the formation of filamentary structure may be key in
resolving these puzzles. New HI surveys of nearby galaxies,
combined with further theoretical studies, promise continuing
important advances.
2002, in Seeing Through the Dust: The Detection of HI and
the Exploration of the ISM in Galaxies, eds. R. Taylor,
T. Landecker, & A. Willis,
(San Francisco: ASP), 295.
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