The Comparison of Physical Properties Derived from Gas and Dust in a Massive Star-Forming Region

Abstract

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.

Accepted by ApJ

References in corpus (7)

• The Boston University-Five College Radio Astronomy Observatory Galactic Ring Survey
• MAMBO Mapping of Spitzer c2d Small Clouds and Cores
• A Minimum Column Density of 1 g cm^-2 for Massive Star Formation
• SCUBA-2: iterative map-making with the Sub-Millimetre User Reduction Facility
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• Multi-wavelength observations of Southern Hot Molecular Cores traced by methanol masers - I. Ammonia and 24 GHz Continuum Data
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Cited by in corpus (14)

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• Kinetic temperature of massive star-forming molecular clumps measured with formaldehyde. III. The Orion Molecular Cloud 1
• Kinetic temperature of massive star forming molecular clumps measured with formaldehyde. II. The Large Magellanic Cloud
• Formation of hydroxylamine on dust grains via ammonia oxidation
• Origins of Scatter in the Relationship Between HCN 1-0 and Dense Gas Mass in the Galactic Center
• Thermal balance and comparison of gas and dust properties of dense clumps in the Hi-GAL survey
• The Green Bank Ammonia Survey: Observations of Hierarchical Dense Gas Structures in Cepheus-L1251
• 3-D CMZ IV: Distinguishing Near vs. Far Distances in the Galactic Center Using Spitzer and Herschel
• Rethinking a Mysterious Molecular Cloud
• Kinetic temperature of massive star-forming molecular clumps measured with formaldehyde V. The massive filament DR21
• The Rosetta Stone Project. II. The correlation between star formation efficiency and L/M indicator for the evolutionary stages of star-forming clumps in post-processed radiative magnetohydrodynamics simulations