Effects of clumping on temperature – I. Externally heated clouds |
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Authors: | S D Doty R A Metzler M L Palotti |
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Institution: | Mt Suhora Observatory of the Pedagogical University, ul. Podchor??ych 2, 30-084 Cracow, Poland;ToruńCentre for Astronomy, Nicholaus Copernicus University, ul. Gagarina 11, 87–100 Toruń, Poland;Instytut Astronomiczny Uniwersytetu Wroc?awskiego, ul. Kopernika 11, 51-622 Wroc?aw, Poland;Astronomical Observatory of the Jagiellonian University, ul. Orla 171, 30–244 Cracow, Poland;INAF–Osservatorio Astronomico di Capodimonte, via Moiariello 16, I-80131, Napoli, Italy |
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Abstract: | We present a study of radiative transfer in dusty, clumpy star-forming regions. A series of self-consistent, 3D, continuum radiative transfer models are constructed for a grid of models parametrized by central luminosity, filling factor, clump radius and face-averaged optical depth. The temperature distribution within the clouds is studied as a function of this parametrization. Among our results, we find that: (i) the effective optical depth in clumpy regions is less than in equivalent homogeneous regions of the same average optical depth, leading to a deeper penetration of heating radiation in clumpy clouds, and temperatures higher by over 60 per cent; (ii) penetration of radiation is driven by the fraction of open sky (FOS) – which is a measure of the fraction of solid angle along which no clumps exist; (iii) FOS increases as clump radius increases and as filling factor decreases; (iv) for values of FOS >0.6–0.8 the sky is sufficiently 'open' that the temperature distribution is relatively insensitive to FOS; (v) the physical process by which radiation penetrates is preferentially through streaming of radiation between clumps as opposed to diffusion through clumps; (vi) filling factor always dominates the determination of the temperature distribution for large optical depths, and for small clump radii at smaller optical depths; (vii) at lower face-averaged optical depths, the temperature distribution is most sensitive to filling factors of 1–10 per cent, in accordance with many observations; (viii) direct shadowing by clumps can be important for distances approximately one clump radius behind a clump. |
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Keywords: | stars: individual: Balloon 090100001 stars: oscillations subdwarfs |
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