Dust temperature and IR emission in high extinction molecular clouds
Abstract
The IR emission from massive, high extinction molecular clouds, heated by a source of energy located near the edge of the cloud has been studied by computing a set of theoretical models.
The dust temperature distribution is practically symmetric around the source of energy. The bulk of the cloud volume contains rather cold grains (Td ≲ 20 K), whose temperature varies by less than a factor of 2. Td is insensitive to the spectral distribution of the energy source, and scales with the source luminosity approximately as L1/5S and with the cloud radius as R2c'5 Variations of the individual dust parameters (a, nd, Q0λ0) do not affect Td, as long as the IR dust opacity (∝ nda2Q0λ0) does not change. The temperature distribution computed assuming τ=0 is a strict upper limit for Td and is in excess by a factor of 2 at most in the cases we have considered. The IR radiation field is strongly anisotropic, with maximum and minimum intensity for inclination angles i = 90° and i = 270°, respectively. Thus, the luminosity and the spectral distribution of the observed radiation vary strongly with i. The brightness distribution is generally characterized by the presence of a narrow component, centered on the source of energy, superposed on a smooth, large scale emission, which contains a considerable fraction (always greater than ∼40%) of the total luminosity. Clouds heated by evolved H II regions show a shell-like structure with possible shifts of the position of the brightness peak with λ.- Publication:
-
Astronomy and Astrophysics
- Pub Date:
- June 1981
- Bibcode:
- 1981A&A....99..289N
- Keywords:
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- Cosmic Dust;
- Infrared Astronomy;
- Interstellar Extinction;
- Molecular Clouds;
- Radiative Heat Transfer;
- Stellar Models;
- Brightness Distribution;
- Protostars;
- Stellar Luminosity;
- Stellar Spectra;
- Stellar Temperature;
- Astrophysics