Astro2020 Science White Paper: Making the Connection between Feedback
  andSpatially Resolved Emission Line Diagnostics
  Crucial progress in our understanding of star formation and feedback will
depend on the ability to obtain spatially resolved spectroscopic observations
of \ion{H}{ii} regions, from which reliable instantaneous measurements of their
physical conditions can be obtained. Acquiring these datasets across full
galactic systems will prove crucial for obtaining population samples that
enable us to understand the time evolution of similar regions, and the
variability of conditions among coeval regions. Separating the spatial and
temporal dependencies in such way for different physical processes involved in
star formation and the injection of feedback is crucial to overcome the inherit
degeneracies associated with observing instantaneous snapshots of a dynamic ISM
at any given time. Emission line diagnostics are at the core of measuring the
physical condition in \ion{H}{ii} regions (e.g. dynamics, SFR, chemical
abundances, dust extinction, ionization and excitation, etc.). These
measurements require high spatial resolution, contiguous coverage across full
galactic systems, and sensitivities significantly deeper than past efforts. The
spatial scale required to resolve the \ion{H}{ii} regions of a few pc is only
attainable in the Local Group where very large sky coverage is necessary.
