Protostars and Planets VI, Heidelberg, July 15-20, 2013
3D Modelling of Clumpy PDRs: the Structure of the ISM in Star Forming Regions
Andree-Labsch, Silke (1. Physikalische Institut, University of Cologne)
Röllig, Markus (1. Physikalische Institut, University of Cologne)
Ossenkopf, Volker (1. Physikalische Institut, University of Cologne)
The interstellar medium (ISM) is permanently irradiated and heated by the UV contribution of massive
stars to the interstellar radiation field. A photon dominated region (PDR) is a region in interstellar space
where the interstellar farUV radiation (with photon energies 6 eV< hν <13.6 eV) dominates the energy
balance and the chemistry of the ISM. It is under investigation whether the radiation field triggers star
formation in the ISM.
The KOSMA-τ PDR model has been developed to simulate the line emission of spherical geometries,
”clumps”, in the ISM. Furthermore, it has been shown that an equivalent superposition of such clumps
(clumpy ensemble) can be used to mimic the structure of the ISM.
Here, by assembling a 3-dimensional compound from different clumpy ensembles, a 3-dimensional model has been set up, enabling us to simulate the emission of clumpy PDRs in arbitrary geometric setups. The model supports analysis of the spatial structure of star forming regions and can simulate the variation of parameters like the UV field strength or the local density for the different clumpy ensembles within one star forming region.
Furthermore, opacities of the clumpy structures are discussed theoretically and the resulting line absorptions are included into the simulations. This step not only refines the fits of observational data, but also improves the simulation of line profiles which can be done with our model.
For testing purposes the new model is used to simulate the main cooling lines and other diagnostics of a well known star forming region, namely the Orion Bar. Through the fit of observational maps and line profiles we are able to constrain the spatial variation of the PDR parameters such as the total mass, different density components and the ambient UV field strength. In addition we can test our understanding of the internal clumpy structure of the ISM and perform a major step towards a fully self-consistent model of typically highly inhomogeneous PDRs.
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