Volume 542, June 2012
GREAT: early science results
Article Number L8
Number of page(s) 5
Section Letters
Published online 10 May 2012

Online material

Appendix A: LVG model of W3(OH)

We reproduced the model of W3(OH) of Cesaroni & Walmsley (1991), which qualitatively models the radio lines of OH, and show here the predictions of this model for the 1834 and 1837 GHz lines. We adopted their parameters, assuming a source size of 2′′ (0.01 pc), a velocity gradient of 200 km s-1 pc-1 and an OH column density between 2 × 1014 cm-2 to 2 × 1016 cm-2. To compare these intensities with the observed values we used a beam size of for SOFIA. In Fig. A.1 two models are shown, with and without an internal radiation field introduced by the present of warm dust. As shown, the latter model underestimates the observed line intensities.

thumbnail Fig. A.1

Results of the LVG models of Cesaroni & Walmsley (1991) showing only the predictions of excitation temperature and line intensity for the 1834 and 1837 GHz lines. The gray dashed area indicates the observed line intensity including the errors. Light green and blue lines correspond to the sum of the hfs lines in each component of the doublet. Upper panels: models with internal radiation field. Lower panels: models without internal radiation field.

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This code is well-adapted for the OH molecule because it includes line-overlap effects, however, for a detailed modeling the radio OH lines need to be taken into account. To perform this modeling for all the sources is beyond the scope of this letter.

Appendix B: RATRAN model of NGC 7538 IRS 1

RATRAN is based on a Monte-Carlo approach to perform radiative transfer calculations (Hogerheijde & van der Tak 2000). It is therefore well-suited for detailed modeling of protostellar envelopes. A radiation field from dust heating was implemented in the models. Note that as shown in Fig. B.1, a line profile can be produced.

thumbnail Fig. B.1

Our RATRAN model of the 1834 GHz and 2514 GHz OH line in emission and in absorption, respectively. Black line shows the observed spectra with baselines removed, the red line shows the model.

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© ESO, 2012

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