The Comparison of Physical Properties Derived from Gas and Dust in a
  Massive Star-Forming Region
  We explore the relationship between gas and dust in massive star-forming
regions by comparing physical properties derived from each. We compare the
temperatures and column densities in a massive star-forming Infrared Dark Cloud
(IRDC, G32.02+0.05), which shows a range of evolutionary states, from quiescent
to active. The gas properties were derived using radiative transfer modeling of
the (1,1), (2,2), and (4,4) transitions of NH3 on the Karl G. Jansky Very Large
Array (VLA), while the dust temperatures and column densities were calculated
using cirrus-subtracted, modified blackbody fits to Herschel data. We compare
the derived column densities to calculate an NH3 abundance, 4.6 x 10^-8. In the
coldest star-forming region, we find that the measured dust temperatures are
lower than the measured gas temperatures (mean and standard deviations T_dust ~
11.6 +/- 0.2 K vs. T_gas ~ 15.2 +/- 1.5 K), which may indicate that the gas and
dust are not well-coupled in the youngest regions (~0.5 Myr) or that these
observations probe a regime where the dust and/or gas temperature measurements
are unreliable. Finally, we calculate millimeter fluxes based on the
temperatures and column densities derived from NH3 which suggest that
millimeter dust continuum observations of massive star-forming regions, such as
the Bolocam Galactic Plane Survey or ATLASGAL, can probe hot cores, cold cores,
and the dense gas lanes from which they form, and are generally not dominated
by the hottest core.
