High-Resolution Far-Infrared Observations of DR 21

Details High-Resolution Far-Infrared Observations of DR 21 High-Resolution Far-Infrared Observations of DR 21

Jul 1995

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1995apj...447..236c&link_type=abstract

Astrophysical Journal v.447, p.236

Astronomy and Astrophysics

Astronomy

11

Ism: Individual Alphanumeric: Dr 21, Ism: Dust, Extinction, Ism: H Ii Regions, Infrared: Ism: Continuum, Ism: Jets And Outflows

Scientific paper

We present new, high angular resolution two-color maps of the compact H II region DR 21 at 50 μm and 100 μm made with the 0.91 m telescope of NASA's Kuiper Airborne Observatory (KAO). From the maps we estimate the total fluxes of DR 21 at 50 μm and 100 μm to be 1.5 × 104 Jy and 3.8 × 104 Jy, respectively.
1. A homogeneous plane-parallel slab model (Model I) is assumed in order to derive dust temperatures and optical depths. This model implies that the dust in DR 21 has relatively small optical depths at 100 μm (τ100 ˜ 0.1) and its temperature ranges from less than 20 K to ˜55 K.
2. A second model is also presented (Model II): a spherically symmetric dust cloud surrounding an O6 star. We used the radiation transfer code developed by Egan, Leung, & Spagna (1988). Our selection criteria for the best fit were based on the best match for both the energy distribution in the 50-1300 μm range and the 100 μm source profile. Assuming the dust properties reported by Mathis, Mezger, & Panagia (1983), and using a mixture of graphite (50% by number) and silicate (50% by number), the best fit to the observations in our modeling with this approach is a spherical dust cloud described by an outer radius of 2.0 pc, an inner radius of 0.1 pc, and a constant dust density distribution. Although this model provides a reasonable fit to the 50-1300 μm flux densities and a marginal fit to the 100 μm profile, the predicted FWHM profiles at 800 and 1100 We present new, high angular resolution two-color maps of the compact H II region DR 21 at 50 μm and 100 μm made with the 0.91 m telescope of NASA's Kuiper Airborne Observatory (KAO). From the maps we estimate the total fluxes of DR 21 at 50 μm and 100 μm to be 1.5 × 104 Jy and 3.8 × 104 Jy, respectively.
1. A homogenous plane-parallel slab model (Model I) is assumed in order to derive dust temperatures and optical depths. This model implies that the dust in DR 21 has relatively small optical depths at 100 μm (τ100 ˜ 0.1) and its temperature ranges from less than 20 K to ˜55 K.
2. A second model is also presented (Model II): a spherically symmetric dust cloud surrounding an O6 star. We used the radiation transfer code developed by Egan, Leung, & Spagna (1988). Our selection criteria for the best fit were based on the best match for both the energy distribution in the 50-1300 μm range and the 100 μm source profile. Assuming the dust properties reported by Mathis, Mezger, & Panagia (1983), and using a mixture of graphite (50% by number) and silicate (50% by number), the best fit to the observations in our modeling with this approach is a spherical dust cloud described by an outer radius of 2.0 pc, an inner radius of 0.1 pc, and a constant dust density distribution. Although this model provides a reasonable fit to the 50-1300 μm flux densities and a marginal fit to the 100 μm profile, the predicted FWHM profiles at 800 and 1100 jim are much broader than those observed with high angular resolution (15" and 19" beams, respectively) as reported in the available literature. Subject headings: dust, extinction H ii regions infrared: ISM: continuum ISM: individual (DR 21) ISM: jets and outflows μm are much broader than those observed with high angular resolution (15" and 19" beams, respectively) as reported in the available literature.

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