All Figures

$\begin{figure} \par\includegraphics[angle=0,width=16.0cm,angle=0]{4991fig1.eps} \end{figure}$ Figure 1: Velocity-integrated intensity maps of [C I] ³P₁-³P₀ emission ( color) overlayed with contours of a) ¹²CO 4-3, b) ¹³CO 2-1, c) ¹²CO 1-0 and d) C¹⁸O 1-0 intensities. All maps are integrated over the range $V_{\rm LSR}=-20$ to -5 km s^-1. Colorscale of the [C I] map and contour levels of all other line intensities are indicated at the top left corner of each panel. The red star denotes the position of the hot spot. All data are shown at a common resolution of 1 $^\prime$ .
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In the text

$\begin{figure} \par\includegraphics[angle=0,width=9.0cm,angle=0]{4991fig2.eps} \end{figure}$ Figure 2: Overlay of [C I] (color) and ¹²CO 4-3 (contours) velocity channel maps of Cepheus B. The colorscale ranges between 1 and 11.6 K km s^-1 and the ¹²CO 4-3 contours are between 5 and 120 K km s^-1 in steps of 15 K km s^-1.
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In the text

$\begin{figure} \par\includegraphics[angle=0,width=7.0cm,angle=0]{4991fig3.eps} \end{figure}$ Figure 3: Observed CI, ¹²CO 4-3, ¹²CO 1-0, ¹³CO 2-1 and [C II] spectra at the position of the molecular hotspot in Cepheus B. The [C II] spectrum is adopted from Boreiko et al. (1990). The ratio of integrated intensities ¹²CO 4-3/¹²CO 1-0 at this position is 1.9. All data are shown at a common resolution of 1 $^\prime$ , except for the [C II] data which has a resolution of 43 $^{\prime \prime }$ .
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In the text

$\begin{figure} \par\includegraphics[angle=0,width=8.0cm,angle=0]{4991fig4a.eps}\includegraphics[angle=0,width=8.0cm,angle=0]{4991fig4b.eps} \end{figure}$ Figure 4: a) Distribution of observed ¹²CO 4-3/¹²CO 1-0 ratio in Cepheus B. b) Distribution of excitation temperatures $T_{\rm ex}$ derived from the ¹²CO 4-3/1-0 line ratio of integrated intensities, assuming LTE. Contours in both panels correspond to integrated intensities of ¹²CO 4-3.
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In the text

$\begin{figure} \par\includegraphics[angle=0,width=7.5cm,angle=0]{4991fig5a.eps}\includegraphics[angle=0,width=8.5cm,angle=0]{4991fig5b.eps} \end{figure}$ Figure 5: a) N(C) vs. N(CO) for independent positions (positions separated by 1 $^\prime$ , i.e., beamwidth) in the map. Typical errors of 15% for N(C) and 10% for N(CO) are shown for one position. b) The C⁰/CO abundance ratio in Cepheus B overlayed with the contours of integrated intensity of C¹⁸O 1-0. We have considered here only those positions for which we have ¹²CO 4-3 data and for which the [C I] and C¹⁸O intensities lie above 3 times their respective rms noise levels.
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In the text

$\begin{figure} \par\includegraphics[angle=0,width=8.0cm,angle=0]{4991fig6.eps} \end{figure}$ Figure 6: Column density ratio of C to CO in Cepheus B. Plotted as in Fig. 5 are independent positions, which are separated by 1 $^\prime$ . Also shown are observed values in other Galactic molecular clouds like NGC 7023 (Gerin et al. 1998), S106 (Schneider et al. 2003), DR 15 (Oka et al. 2001), MCLD 123.5+24.9 (Bensch et al. 2003), High Latitude Clouds (Ingalls et al. 1997), NGC 1333 (Oka et al. 2004), $\rho$ Oph (Kamegai et al. 2003), W3Main (Kramer et al. 2004) and Orion (Ikeda et al. 2002). The points corresponding to GMCs are taken from Plume et al. (1999) in which [C I] data of Cep A, S 140, NGC 2024 and W3 were presented. The red drawn line corresponds to the parameter derived by fitting only the Cepheus B data. Typical errors of 15% for N(C)/N(CO) and 10% for N(H₂) are shown for one position. The blue line is the result of fitting data points for all previous observations.
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In the text

$\begin{figure} \par\includegraphics[angle=0,width=8.0cm,angle=0]{4991fig7.eps} \end{figure}$ Figure 7: FUV intensity distribution (red contours) in Cepheus B estimated from the FIR fluxes measured by IRAS, overlayed with [C I] integrated intensities (in color). Contour levels of the FUV intensity are indicated at the top left corner. The intensity scale for the [C I] map are the same as in Fig. 1. White stars denote HD 217086 (north) and HD 217061, Crosses denote the NIR sources A-NIR (south) and B-NIR and the filled triangle denotes the location of the hot spot.
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In the text

$\begin{figure} \par\includegraphics[angle=0,width=9.0cm,angle=0]{4991fig8.eps} \end{figure}$ Figure 8: Results from the PDR models for external FUV fields of $\chi = 10^3$ a) and $\chi = 10^2$ , expressed in Draine units b). Contours show integrated intensity line ratios of CI/¹²CO 4-3 and CI/¹³CO 2-1. The range of observed values is shown: 0.3-0.7 for CI/¹³CO 2-1, 0.2-0.6 for CI/¹²CO 4-3. We consider only positions for which the C/CO abundance ratio has been estimated. Both ratios suggest that the volume densities on an average lie between 10⁴ and 10⁵ cm^-3.
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In the text

$\begin{figure} \par\includegraphics[angle=0,width=9.0cm,angle=0]{4991fig9.eps} \end{figure}$ Figure 9: Abundance profiles of C⁰ and CO calculated by the KOSMA- $\tau$ PDR model for two clumps with masses 1 $M_{\rm\odot }$ and 0.001 $M_{\rm\odot }$ . The x-axis is given in units of the relative depth $d/R_{\rm tot}$ . A value of 1 denotes the center of the cloud. The FUV field strength is 10²in Draine units.
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In the text

$\begin{figure} \par\includegraphics[angle=0,width=8.0cm,angle=0]{4991fig10.eps} \end{figure}$ Figure 10: KOSMA- $\tau$ PDR model interpretation of the observed C/CO vs. N(H₂) anti-correlation. For comparison results of face-on homogeneous plane-parallel models are also shown. Drawn lines correspond to models the input parameters for which are marked at the bottom left corner. $M_{\rm cl}$ corresponds to mass of an individual clump. $M_{\rm beam}$ shown along the upper x-axis is the mass of gas in the 60 $^{\prime \prime }$ beam. The number of clumps in the beam is given by $M_{\rm beam}$ / $M_{\rm cl}$ .
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In the text

$\begin{figure} \par\includegraphics[angle=0,width=9.0cm,angle=0]{4991fig2.eps} \end{figure}$	Figure 2: Overlay of [C I] (color) and ¹²CO 4-3 (contours) velocity channel maps of Cepheus B. The colorscale ranges between 1 and 11.6 K km s^-1 and the ¹²CO 4-3 contours are between 5 and 120 K km s^-1 in steps of 15 K km s^-1.
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$\begin{figure} \par\includegraphics[angle=0,width=8.0cm,angle=0]{4991fig4a.eps}\includegraphics[angle=0,width=8.0cm,angle=0]{4991fig4b.eps} \end{figure}$	Figure 4: a) Distribution of observed ¹²CO 4-3/¹²CO 1-0 ratio in Cepheus B. b) Distribution of excitation temperatures $T_{\rm ex}$ derived from the ¹²CO 4-3/1-0 line ratio of integrated intensities, assuming LTE. Contours in both panels correspond to integrated intensities of ¹²CO 4-3.
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$\begin{figure} \par\includegraphics[angle=0,width=9.0cm,angle=0]{4991fig9.eps} \end{figure}$	Figure 9: Abundance profiles of C⁰ and CO calculated by the KOSMA- $\tau$ PDR model for two clumps with masses 1 $M_{\rm\odot }$ and 0.001 $M_{\rm\odot }$ . The x-axis is given in units of the relative depth $d/R_{\rm tot}$ . A value of 1 denotes the center of the cloud. The FUV field strength is 10²in Draine units.
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