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Modelling of clumpy photon dominated regions

Published online by Cambridge University Press:  04 October 2008

C. Kramer ,
S. Aalto ,
R. Simon ,
M. Cubick ,
M. Röllig ,
V. Ossenkopf ,
C. Kramer  and
J. Stutzki
M. Cubick*
Affiliation:
I. Physikalisches Institut, Universität zu Köln, Zülpicher Straße 77, 50937 Köln, Germany
M. Röllig
Affiliation:
I. Physikalisches Institut, Universität zu Köln, Zülpicher Straße 77, 50937 Köln, Germany
V. Ossenkopf
Affiliation:
I. Physikalisches Institut, Universität zu Köln, Zülpicher Straße 77, 50937 Köln, Germany SRON Netherlands Institute for Space Research, PO Box 800, 9700 AV Groningen, The Netherlands
C. Kramer
Affiliation:
I. Physikalisches Institut, Universität zu Köln, Zülpicher Straße 77, 50937 Köln, Germany
J. Stutzki
Affiliation:
I. Physikalisches Institut, Universität zu Köln, Zülpicher Straße 77, 50937 Köln, Germany
*
[email protected]
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Abstract

Observations of the interstellar medium (ISM) reveal its fractalstructure over a large range of scales. The quantitative description shows that the ISM consists mainly of surfaces, so that the stellar UV-radiation can deeply penetrate intothe ISM and in consequence dominates its physical and chemical conditions. Thus, the bulk of the ISM can be identified as photon dominated regions (PDRs). A simple model with the proper fractal characteristics is that of an ensemble of spherical clumps with a power-law mass spectrum and a power-law mass-size relation. Hence, we model the FIR line emission of the molecular gasby the integrated emission of such an ensemble, calculating the emission of individual clumps with the KOSMA-τ PDR code. This clumpy PDR-model, with observationally constrained parameters, is fitted to the CO, [C i], and [O i] emission along the Galactic plane as observed by the FIRAS instrument abord the COBE satellite. The FIR line intensity distribution with Galactic longitude is reproduced within factors of about 2. The predicted [C ii] 158 μm line intensity and FIR continuum emission also coincide with the observations.

Type
Research Article
Information
European Astronomical Society Publications Series , Volume 31: Far-Infrared Workshop 2007 , 2008 , pp. 19 - 22
Copyright
© EAS, EDP Sciences, 2008

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References

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