All Figures

$\begin{figure} \par\includegraphics[angle=-90,width=12.3cm,clip]{m3708f1.ps} % \end{figure}$ Figure 1: Overview of the ISO-LWS data for a selection of the ortho-H₂O 2₂₁-1₁₀, 4₂₃-4₁₄, 3₀₃-2₁₂, and 2₁₂-1₀₁ lines at 108.1 $\mu$ m, 132.4 $\mu$ m, 174.6 $\mu$ m, and 179.5 $\mu$ m respectively, in a) AFGL 2591, b) NGC 7538 IRS9, c) W 3 IRS5, d) S 140 IRS1, and e) NGC 7538 IRS1. The vertical markers indicate the (tentative) detections. All lines have been corrected for the $V_{\rm {LSR}}$ of the source and the resolution of the spectra is $\Delta V\sim 30$ km s^-1. The vertical dotted lines indicate the positions of the H₂O lines if they are at the $V_{\rm {LSR}}$ of the source. The deviations of the (tentative) detections from the dotted lines are about the spectral resolution. The ortho-H₂O 2₂₁-1₁₀ line has not been observed toward S 140 IRS1. Note that the flux scale in the panel of the 3₀₃-2₁₂ line in S 140 IRS1 covers twice as large a range as in all other panels.
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In the text

$\begin{figure} \par\includegraphics[angle=-90,width=12.2cm,clip]{m3708f2.ps} \end{figure}$ Figure 2: Continuum subtracted spectra of the CO J=7-6 lines (JCMT) compared with the H₂O 1 ₁₀-1₀₁ lines (SWAS). The CO lines have been shifted upwards by 2 K for clarity. The H₂O lines have been multiplied by a factor of 20, except that for AFGL 2591 which is multiplied by 80. Both spectra have been binned to a spectral resolution of $\sim$ 0.9 km s^-1 (see text).
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In the text

$\begin{figure} \par\includegraphics[width=7.8cm,clip]{m3708f3.ps} % \end{figure}$ Figure 3: Dust temperature (full lines) and density (dashed lines) profiles toward four of our sources.
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In the text

$\begin{figure} \par\includegraphics[angle=-90,width=12.6cm,clip]{m3708f4.ps} % \end{figure}$ Figure 4: H₂O abundances as functions of distance from the central star in the molecular envelope of AFGL 2591 for different chemical scenarios, using the physical structure for AFGL 2591 as derived by van der Tak et al. (2000b). The number in each panel refers to the scenario number in Table 3.
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In the text

$\begin{figure} \par\includegraphics[width=6.9cm,clip]{m3708f5.ps} % \end{figure}$ Figure 5: a) The SWS data for the $\nu _2$ ro-vibrational band in absorption toward AFGL 2591 as presented in Boonman & van Dishoeck (2003). b) Model spectrum based on chemical scenario 8, including ice evaporation and freeze-out. c) Model spectrum based on chemical scenario 1, without ice evaporation and without freeze-out. d) Ratio of the absolute differences between the model spectrum and the SWS data for panel c) and those for panel b). This ratio demonstrates that the scenario with ice evaporation (scenario 8) matches the observations much better than that without ice evaporation (scenario 1) over almost the entire wavelength range.
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In the text

$\begin{figure} \par\includegraphics[width=7.4cm,clip]{m3708f6.ps} % \end{figure}$ Figure 6: Comparison of the predicted values for the different chemical scenarios with the observed values for AFGL 2591 (Table 4). For the ISO-SWS and -LWS data the $\chi ^2$ is presented, whereas for the SWAS data the signed standard deviation is shown (see text). The minimum absolute deviation corresponds to the chemical scenario that reproduces all observed H₂O lines best. a) Comparison of the deviation for the LWS and SWAS data. b) The deviation for the SWS data compared to a blow-up of that for the LWS data for scenarios 3-9. The LWS data have been divided by 2. c) Blow-up of the deviation for the SWAS data shown in panel a) for scenarios 3-9 compared to the deviation in case the observed SWAS line flux is a factor of 2 higher (filled stars).
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In the text

$\begin{figure} \par\includegraphics[angle=-90,width=7.8cm,clip]{m3708f7.ps} % \end{figure}$ Figure 7: Comparison of the predicted values for the different chemical scenarios with the observed values for NGC 7538 IRS9 (Table 5). For the SWS and LWS data the $\chi ^2$ is presented, whereas for the SWAS data the signed standard deviation is shown (see text). The minimum absolute deviation corresponds to the chemical scenario that reproduces all observed H₂O lines best. a) Comparison of the deviation for the LWS and SWS data. The LWS data have been divided by 3. b) The deviation for the SWAS data compared to a blow-up of that for the LWS data for scenarios 3-9. (Table 5).
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In the text

$\begin{figure} \par\includegraphics[width=6.9cm,clip]{m3708f8.ps} % \end{figure}$ Figure 8: a) The SWS spectrum toward NGC 7538 IRS9 as presented in Boonman & van Dishoeck (2003). b) Model spectrum based on chemical scenario 5, including ice evaporation and freeze-out (using b=2.5 km s^-1). c) Model spectrum based on chemical scenario 1, without ice evaporation and without freeze-out (using b=2.5 km s^-1).
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In the text

$\begin{figure} \par\includegraphics[angle=-90,width=7.9cm,clip]{m3708f9.ps} % \end{figure}$ Figure 9: Comparison of the predicted values for the different chemical scenarios with the observed values for W 3 IRS5 (Table 6). For the SWS and LWS data the $\chi ^2$ is presented, whereas for the SWAS data the signed standard deviation is shown (see text). The minimum absolute deviation corresponds to the chemical scenario that reproduces all observed H₂O lines best. a) Comparison of the deviation for the LWS and SWAS data. b) The deviation for the SWS data compared to a blow-up of that for the LWS data for scenarios 3-9.
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In the text

$\begin{figure} \par\includegraphics[width=6.45cm,clip]{m3708f10.ps} % \end{figure}$ Figure 10: a) The SWS spectrum toward W 3 IRS5 as presented in Boonman & van Dishoeck (2003). b) Model spectrum based on chemical scenario 5, including ice evaporation and freeze-out (using b=1.5 km s^-1). c) Model spectrum based on chemical scenario 1, without ice evaporation and without freeze-out (using b=1.5 km s^-1).
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In the text

$\begin{figure} \par\includegraphics[angle=-90,width=7.9cm,clip]{m3708f11.ps} % \end{figure}$ Figure 11: Comparison of the predicted values for the different chemical scenarios with the observed values for S 140 IRS1 (Table 7). For the SWS and LWS data the $\chi ^2$ is presented, whereas for the SWAS data the signed standard deviation is shown (see text). The minimum absolute deviation corresponds to the chemical scenario that reproduces all observed H₂O lines best. a) The deviation for the LWS data. b) Comparison of the deviation for the SWS and SWAS data. The SWAS data have been divided by 2.
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In the text

$\begin{figure} \par\includegraphics[width=6.9cm,clip]{m3708f12.ps} % \end{figure}$ Figure 12: a) The SWS spectrum toward S 140 IRS1 as presented in Boonman & van Dishoeck (2003). b) Model spectrum based on chemical scenario 5, including ice evaporation and freeze-out (using b=1.0 km s^-1). c) Model spectrum based on chemical scenario 1, without ice evaporation and without freeze-out (using b=1.0 km s^-1).
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In the text

$\begin{figure} \par\includegraphics[angle=-90,width=12.2cm,clip]{m3708f2.ps} \end{figure}$	Figure 2: Continuum subtracted spectra of the CO J=7-6 lines (JCMT) compared with the H₂O 1 ₁₀-1₀₁ lines (SWAS). The CO lines have been shifted upwards by 2 K for clarity. The H₂O lines have been multiplied by a factor of 20, except that for AFGL 2591 which is multiplied by 80. Both spectra have been binned to a spectral resolution of $\sim$ 0.9 km s^-1 (see text).
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$\begin{figure} \par\includegraphics[width=7.8cm,clip]{m3708f3.ps} % \end{figure}$	Figure 3: Dust temperature (full lines) and density (dashed lines) profiles toward four of our sources.
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$\begin{figure} \par\includegraphics[angle=-90,width=12.6cm,clip]{m3708f4.ps} % \end{figure}$	Figure 4: H₂O abundances as functions of distance from the central star in the molecular envelope of AFGL 2591 for different chemical scenarios, using the physical structure for AFGL 2591 as derived by van der Tak et al. (2000b). The number in each panel refers to the scenario number in Table 3.
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$\begin{figure} \par\includegraphics[width=6.9cm,clip]{m3708f8.ps} % \end{figure}$	Figure 8: a) The SWS spectrum toward NGC 7538 IRS9 as presented in Boonman & van Dishoeck (2003). b) Model spectrum based on chemical scenario 5, including ice evaporation and freeze-out (using b=2.5 km s^-1). c) Model spectrum based on chemical scenario 1, without ice evaporation and without freeze-out (using b=2.5 km s^-1).
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$\begin{figure} \par\includegraphics[width=6.45cm,clip]{m3708f10.ps} % \end{figure}$	Figure 10: a) The SWS spectrum toward W 3 IRS5 as presented in Boonman & van Dishoeck (2003). b) Model spectrum based on chemical scenario 5, including ice evaporation and freeze-out (using b=1.5 km s^-1). c) Model spectrum based on chemical scenario 1, without ice evaporation and without freeze-out (using b=1.5 km s^-1).
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$\begin{figure} \par\includegraphics[width=6.9cm,clip]{m3708f12.ps} % \end{figure}$	Figure 12: a) The SWS spectrum toward S 140 IRS1 as presented in Boonman & van Dishoeck (2003). b) Model spectrum based on chemical scenario 5, including ice evaporation and freeze-out (using b=1.0 km s^-1). c) Model spectrum based on chemical scenario 1, without ice evaporation and without freeze-out (using b=1.0 km s^-1).
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