All Figures

$\begin{figure} \par\resizebox{8.8cm}{!}{\includegraphics{5918fig1.eps}}\end{figure}$ Figure 1: Common geometrical setups of a model PDR. The surface of any plane-parallel or spherical cloud is illuminated either a) uni-directional or b) isotropically.
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In the text

$\begin{figure} \par\resizebox{8.8cm}{!}{\includegraphics{5918fig2.eps}}\end{figure}$ Figure 2: Comparison of attenuation of the mean intensity for the case of an uni-directional and isotropically illuminated medium. The solid line gives the attenuation due to uni-directional illumination, while the dashed line gives the attenuation for an isotropic FUV radiation where $\tau$ means the optical depth perpendicular to the surface of the cloud.
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In the text

$\begin{figure} \par\resizebox{8.8cm}{!}{\includegraphics{5918fig3.eps}}\end{figure}$ Figure 3: H₂ photo-dissociation rates resulting from uni-directional FUV illuminated clouds compared to an isotropic illumination. The results from isotropic models are plotted vs. the perpendicular $A_{\rm V}$ and vs. $A_{\rm V,eff}$ .
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In the text

$\begin{figure} \par\includegraphics[width=17cm,clip]{5918fig4.eps}\end{figure}$ Figure 4: The influence of the cosmic ray ionization rate on the chemical structure of a model cloud. The left panel shows results for Model F1 (n=10³ cm^-3, $\chi =10$ ), the right panel gives results for 10 times higher densities (n=10⁴ cm^-3, $\chi =10$ ). The solid lines give the results for a cosmic ray ionization rate of Helium, enhanced by a factor 4, the dashed lines are for the lower ionization rate. The different colors denote different chemical species. The most prominent differences are highlighted with colored arrows.
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In the text

$\begin{figure} \par\resizebox{8.8cm}{!}{\includegraphics{5918fig5.eps}}\end{figure}$ Figure 5: Comparison between model codes with (dashed line) and without (solid line) excited molecular hydrogen, H₂^*. The abundance profile of CH is plotted for both models against $A_{\rm V,eff}$ . Benchmark model F3 has a high density ( n=10^5.5 cm^-3) and low FUV intensity ( $\chi =10$ ).
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In the text

$\begin{figure} \par\resizebox{8.8cm}{!}{\includegraphics{5918fig6.eps}}\end{figure}$ Figure 6: The density profile of atomic carbon for the benchmark model F2 (low density, high FUV, $T={\rm const.}=50$ K, as discussed in Sect. 4). The solid curve results from a constant dissociation by CR induced secondary photons (implicitely assuming T=300 K), the dashed curve shows the influence of a temperature dependent dissociation, i.e. the corresponding dissociation rate was corrected by a factor of $\left(T/300~{\rm K}\right)^{1.17}$ with T=50 K.
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In the text

$\begin{figure} \par\includegraphics[width=14cm,clip]{5918fi7a.eps}\par\includegraphics[width=14cm,clip]{5918fi7b.eps}\end{figure}$ Figure 7: Model F1 (n=10³ cm^-3, $\chi =10$ ): comparison between the density profiles of C⁺ ( top), C ( middle), and CO ( bottom) before ( top) and after ( bottom) the comparison study. The vertical lines indicate the code dependent scatter. For C and CO they indicate the depths at which the maximum density is reached, while for C⁺ they indicate the depths at which the density dropped by a factor of 10. Dashed lines indicate pre-benchmark results, while solid lines are post-benchmark.
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In the text

$\begin{figure} \par\includegraphics[width=17 cm,clip]{5918fig8.eps}\end{figure}$ Figure 8: Model F1 (n=10³ cm^-3, $\chi =10$ ): the photo-dissociation rates of H₂ ( left column), of CO ( middle column) and the photo-ionization rate of C ( right column) after the comparison study.
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In the text

$\begin{figure} \par\resizebox{8.8cm}{!}{\includegraphics{5918fig9.eps}}\end{figure}$ Figure 9: Model F1 (n=10³ cm^-3, $\chi =10$ ) The H-H₂ transition zone after the comparison study. Plotted is the number density of atomic and molecular hydrogen as a function of $A_{\rm V,eff}$ . The vertical lines denote the range of the predicted transition depths for pre- and post-benchmark results (dashed and solid lines respectively).
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In the text

$\begin{figure} \par\includegraphics[width=14cm]{5918fi10.eps}\end{figure}$ Figure 10: Model F4 ( n=10^5.5 cm^-3, $\chi =10^5$ ): the post-benchmark photo-dissociation rates of H₂ ( left column), of CO ( middle column) and the photo-ionization rate of C ( right column) ( upper plot).
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In the text

$\begin{figure} \par\includegraphics[width=15.5cm,clip]{5918f11a.eps}\par\includegraphics[width=15.5cm,clip]{5918f11b.eps}\end{figure}$ Figure 11: Model F4 ( n=10^5.5 cm^-3, $\chi =10^5$ ): The upper panel shows the post-benchmark results for the H and H₂ densities. The lower panel shows the post-benchmark density profiles of C⁺, C, and CO. The vertical gray lines in both panels indicate the pre-to-post changes.
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In the text

$\begin{figure} \par\resizebox{8.8cm}{!}{\includegraphics{5918fi12.eps}}\end{figure}$ Figure 12: Model V2 (n=10³ cm^-3, $\chi =10^5$ ): the plot shows the post-benchmark results for the gas temperature.
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In the text

$\begin{figure} \par\includegraphics[width=15cm,clip]{5918f13a.eps} \includegraphics[width=15cm,clip]{5918f13b.eps} \end{figure}$ Figure 13: Model V2 (n=10³ cm^-3, $\chi =10^5$ ): the post-benchmark photo-dissociation rates of H₂ ( left column), and the photo-ionization rate of C ( right column) ( upper plot). The lower plots shows the H and H₂ densities.
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In the text

$\begin{figure} \par\mbox{\includegraphics[width=9cm]{5918f14a.eps}\hspace*{5mm} ... ...14c.eps}\hspace*{5mm} \includegraphics[width=9cm]{5918f14d.eps} } \end{figure}$ Figure 14: Model V2 (n=10³ cm^-3, $\chi =10^5$ ): the post-benchmark results for the densities of C⁺ ( top left), the densities of C ( top right), and the densities of CO ( bottom left) and O and O₂ ( bottom right).
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In the text

$\begin{figure} \par\resizebox{8.8cm}{!}{\includegraphics{5918fi15.eps}} \end{figure}$ Figure 15: Model V2 (n=10³ cm^-3, $\chi =10^5$ ): the plot shows the post-benchmark surface brightnesses of the main fine-structure cooling lines: [CII] 158 $\mu$ m, [OI] 63, and 146 $\mu$ m, and [CI] 610 and 370 $\mu$ m.
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In the text

$\begin{figure} \par\includegraphics[width=15cm]{5918fi16.eps} \end{figure}$ Figure 16: Model V2 (n=10³ cm^-3, $\chi =10^5$ ): the post-benchmark local emissivities of [OI] 63 ${\rm\mu m}$ ( left column), and [CI] 310 ${\rm\mu m}$ ( right column).
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In the text

$\begin{figure} \par\resizebox{8.8cm}{!}{\includegraphics{5918fig1.eps}}\end{figure}$	Figure 1: Common geometrical setups of a model PDR. The surface of any plane-parallel or spherical cloud is illuminated either a) uni-directional or b) isotropically.
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$\begin{figure} \par\resizebox{8.8cm}{!}{\includegraphics{5918fig2.eps}}\end{figure}$	Figure 2: Comparison of attenuation of the mean intensity for the case of an uni-directional and isotropically illuminated medium. The solid line gives the attenuation due to uni-directional illumination, while the dashed line gives the attenuation for an isotropic FUV radiation where $\tau$ means the optical depth perpendicular to the surface of the cloud.
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$\begin{figure} \par\resizebox{8.8cm}{!}{\includegraphics{5918fig3.eps}}\end{figure}$	Figure 3: H₂ photo-dissociation rates resulting from uni-directional FUV illuminated clouds compared to an isotropic illumination. The results from isotropic models are plotted vs. the perpendicular $A_{\rm V}$ and vs. $A_{\rm V,eff}$ .
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$\begin{figure} \par\resizebox{8.8cm}{!}{\includegraphics{5918fig5.eps}}\end{figure}$	Figure 5: Comparison between model codes with (dashed line) and without (solid line) excited molecular hydrogen, H₂^*. The abundance profile of CH is plotted for both models against $A_{\rm V,eff}$ . Benchmark model F3 has a high density ( n=10^5.5 cm^-3) and low FUV intensity ( $\chi =10$ ).
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$\begin{figure} \par\includegraphics[width=17 cm,clip]{5918fig8.eps}\end{figure}$	Figure 8: Model F1 (n=10³ cm^-3, $\chi =10$ ): the photo-dissociation rates of H₂ ( left column), of CO ( middle column) and the photo-ionization rate of C ( right column) after the comparison study.
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$\begin{figure} \par\resizebox{8.8cm}{!}{\includegraphics{5918fig9.eps}}\end{figure}$	Figure 9: Model F1 (n=10³ cm^-3, $\chi =10$ ) The H-H₂ transition zone after the comparison study. Plotted is the number density of atomic and molecular hydrogen as a function of $A_{\rm V,eff}$ . The vertical lines denote the range of the predicted transition depths for pre- and post-benchmark results (dashed and solid lines respectively).
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$\begin{figure} \par\includegraphics[width=14cm]{5918fi10.eps}\end{figure}$	Figure 10: Model F4 ( n=10^5.5 cm^-3, $\chi =10^5$ ): the post-benchmark photo-dissociation rates of H₂ ( left column), of CO ( middle column) and the photo-ionization rate of C ( right column) ( upper plot).
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$\begin{figure} \par\includegraphics[width=15.5cm,clip]{5918f11a.eps}\par\includegraphics[width=15.5cm,clip]{5918f11b.eps}\end{figure}$	Figure 11: Model F4 ( n=10^5.5 cm^-3, $\chi =10^5$ ): The upper panel shows the post-benchmark results for the H and H₂ densities. The lower panel shows the post-benchmark density profiles of C⁺, C, and CO. The vertical gray lines in both panels indicate the pre-to-post changes.
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$\begin{figure} \par\resizebox{8.8cm}{!}{\includegraphics{5918fi12.eps}}\end{figure}$	Figure 12: Model V2 (n=10³ cm^-3, $\chi =10^5$ ): the plot shows the post-benchmark results for the gas temperature.
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$\begin{figure} \par\includegraphics[width=15cm,clip]{5918f13a.eps} \includegraphics[width=15cm,clip]{5918f13b.eps} \end{figure}$	Figure 13: Model V2 (n=10³ cm^-3, $\chi =10^5$ ): the post-benchmark photo-dissociation rates of H₂ ( left column), and the photo-ionization rate of C ( right column) ( upper plot). The lower plots shows the H and H₂ densities.
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$\begin{figure} \par\mbox{\includegraphics[width=9cm]{5918f14a.eps}\hspace{5mm} ... ...14c.eps}\hspace{5mm} \includegraphics[width=9cm]{5918f14d.eps} } \end{figure}$	Figure 14: Model V2 (n=10³ cm^-3, $\chi =10^5$ ): the post-benchmark results for the densities of C⁺ ( top left), the densities of C ( top right), and the densities of CO ( bottom left) and O and O₂ ( bottom right).
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$\begin{figure} \par\resizebox{8.8cm}{!}{\includegraphics{5918fi15.eps}} \end{figure}$	Figure 15: Model V2 (n=10³ cm^-3, $\chi =10^5$ ): the plot shows the post-benchmark surface brightnesses of the main fine-structure cooling lines: [CII] 158 $\mu$ m, [OI] 63, and 146 $\mu$ m, and [CI] 610 and 370 $\mu$ m.
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$\begin{figure} \par\includegraphics[width=15cm]{5918fi16.eps} \end{figure}$	Figure 16: Model V2 (n=10³ cm^-3, $\chi =10^5$ ): the post-benchmark local emissivities of [OI] 63 ${\rm\mu m}$ ( left column), and [CI] 310 ${\rm\mu m}$ ( right column).
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