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Appendix A: Herschel observations

Appendix B: Emission line contamination of o-NH₂ towards W49N

The o-NH₂ absorption towards W49N is contaminated by an emission line in the same sideband from the source, a more complicated situation than an emission line from the other sideband. In Fig. B.3 an emission line is clearly visible around 47 km s^-1 in the o-NH₂ spectrum. Here, the intensities have been normalised to the continuum in single sideband as T_A/T_C-1 assuming a sideband gain ratio of unity where T_A is the observed intensity and T_C is the SSB continuum as measured in line-free regions in the spectra. We identify the emission line as a blend of three unresolved hfs components of NO , F = 10.5 − 9.5, 9.5–8.5, and 8.5–9.5, at 952.464201 GHz (weighted mean frequency, cf. Varberg et al. 1999). The emission line appearing near 142 km s^-1 in this figure is consequently identified as the hfs blend in the lower half of the same spin-rotation doublet of NO at an average rest frequency of 952.145441 GHz. The PRISMAS observations have also found three additional NO lines in W49N shown in Fig. B.2, each one consisting of unresolved hfs components, while no emission of NO is found in G10.6 − 0.4.

Since the two NO lines seen in Fig. B.3 have almost equal line strength, and are also observed with the same instrument in the same band, we have used the observed 952.145 GHz transition as a template to remove the interfering NO line at 952.464 GHz from the o-NH₂ absorption. In order to do this we use (B.1)to calculate the normalised SSB intensity T_norm in K, where T_C is the SSB continuum, and T_NO is the intensity of the NO line (T_A − T_C,DSB). The model NO line, shown in Fig. B.1, is then moved to the velocity of the emission line. The resulting absorption line spectrum of o-NH₂ towards W49N with removed NO emission is shown in green in Fig. B.3.

	Fig. B.1 W49N: model of the 952.464 GHz NO line to be removed from the o-NH2 absorption lines. The model is using the NO 952.145 GHz emission line observed at vLSR = +7.7 km s-1 and only shifted in velocity to a vLSR of +43.5 km s-1 corresponding to a vLSR of +7.7 km s-1 for that line.
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	Fig. B.2 W49N: double sideband WBS spectra of four NO emission lines from the source itself. Each NO line consists of 3 hfs components, with quatum numbers (651 GHz), J = 6.5f → 5.5f (652 GHz), J = 7.5e → 6.5e (752 GHz), and J = 9.5e → 8.5e (952 GHz). The emission line at  − 18 km s-1 blended with NO 651.433 GHz is SO 1111–1110.
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Fig. B.3 NO emission from W49N in the line-of-sight o-NH2 absorption: normalised SSB spectrum of o-NH2. The emission line at 142 km s-1 is from NO at ν0 = 952.145 GHz. The NO ν0 = 952.464 GHz emission feature is seen at 47 km s-1 in the o-NH2 absorption. The two NO lines have similar line strengths. The red line shows the SSB normalised o-NH2 line without removal of the NO-line, and the green shows the spectra with removed NO-line.

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Appendix C: Hyperfine structure components

Appendix D: Method II results

Appendix E: Method III results

Appendix F: Results for CN and HNC

Appendix G: Figures

	Fig. G.1 G10.6−0.4 (W31C): double sideband spectra of NH, ortho-NH2, ortho- and para-14NH3, ortho-15NH3, and NH+ over the LSR velocity range –50 to 85 km s-1.
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	Fig. G.2 G10.6−0.4 (W31C): normalised ammonia and the ammonia isotopologue 15NH3. (The emission line at vLSR ≈ 41 and 72 km s-1 is an SO2 line from the upper sideband.)
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	Fig. G.3 W49N: fits of method II to NH and o-NH2, and their observed spectra. Residuals are found at the bottom. Template spectrum is o-NH3 at 572 GHz.
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	Fig. G.4 W49N: fits of method II to NH, o-NH2 and o-NH3, and their observed spectra. Residuals are found at the bottom. Template spectrum is CH at 532 GHz.
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	Fig. G.5 G10.6−0.4 (W31C): fits of method II to NH and o-NH2, and their observed spectra. Residuals are found at the bottom. Template spectrum is o-NH3 at 572 GHz.
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	Fig. G.6 G10.6−0.4 (W31C): fits of method II to NH, o-NH2 and o-NH3, and their observed spectra. Residuals are found at the bottom. Template spectrum is CH at 532 GHz.
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	Fig. G.7 W49N: method III (XCLASS) fits to the nitrogen hydrides and CH.
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	Fig. G.8 G10.6−0.4 (W31C): method III (XCLASS) fits to the nitrogen hydrides and CH.
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	Fig. G.9 Comparison of absorption lines towards W49N and G10.6−0.4. The intensities have been normalised to single sideband continuum. An NO emission line from the source (952.464 GHz) has been removed from the o-NH2 spectrum (see Sect. B.)
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	Fig. G.10 Comparison of absorption lines towards W49N and G10.6−0.4. The intensities have been normalised to single sideband continuum.
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Appendix H: Comparison plots of different methods

In Fig. H.1 we plot the resulting column densities from our three different methods.

Note that since Method I and Method III use Gaussians with smaller line widths than the velocity bins of Method II towards G10.6−0.4, the number of velocity components is not the same in this source. The +33 km s^-1 component towards W49N is not used in Method II, which on the other hand models a velocity bin that is difficult to fit using Gaussians in Method I and III (50–57 km s^-1). The comparison of the nitrogen hydrides vs. CH in W49N, in two of the four velocity bins, shows the only cases in which the results do not agree reasonably well between the methods. The resulting CH column densities also show a larger

spread between the methods than the other species. The reason is not fully understood, but is probably caused by the different approaches to the CH modelling. Method II uses the deconvolved CH spectra as a template for the nitrogen hydrides and is thereby trying to fit the broader CH absorption to the more narrow features of the nitrogen hydrides with moderate success. The other two methods use an opposite approach: they use the output of the fitting of the nitrogen hydrides as an input to CH to fit Gaussians only in the same parts in velocity space, and are thereby trying to fit narrow features to the broader CH absorption. The fit is good in some parts of the velocity space, and very bad in the velocity space in which CH has absorption but the nitrogen hydrides do not, which is expected.

	Fig. H.1 Column density comparison plots. The results from all three methods are plotted. The scatter in the results can be considered as an estimate of the errors.
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	Fig. H.1 continued.
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	Fig. H.1 continued.
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	Fig. H.1 continued.
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© ESO, 2012