Herschel observations of EXtra-Ordinary Sources (HEXOS): Detection of hydrogen fluoride in absorption towards Orion KL*

Abstract

We report a detection of the fundamental rotational transition of hydrogen fluoride in absorption towards Orion KL using Herschel/HIFI. After the removal of contaminating features associated with common molecules (“weeds”), the HF spectrum shows a P-Cygni profile, with weak redshifted emission and strong blue-shifted absorption, associated with the low-velocity molecular outflow. We derive an estimate of 2.9 × 1013 cm−2 for the HF column density responsible for the broad absorption component. Using our best estimate of the H2 column density within the low-velocity molecular outflow, we obtain a lower limit of ∼1.6 × 10−10 for the HF abundance relative to hydrogen nuclei, corresponding to ∼0.6% of the solar abundance of fluorine. This value is close to that inferred from previous ISO observations of HF J = 2−1 absorption towards Sgr B2, but is in sharp contrast to the lower limit of 6 × 10−9 derived by Neufeld et al. for cold, foreground clouds on the line of sight towards G10.6-0.4.

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@inproceedings{Phillips2010HerschelOO, title={Herschel observations of EXtra-Ordinary Sources (HEXOS): Detection of hydrogen fluoride in absorption towards Orion KL*}, author={Tom G. Phillips and Edwin A. Bergin and Dariusz C. Lis and David A . Neufeld and Tom A. Bell and Shiya Wang and Nathan R. Crockett and Pierre J. Encrenaz and M. Gerin and Thomas F Giesen and Javier R. Goicoechea and Paul F. Goldsmith and Phillip G. Martin and G . J . Melnick and Karl M Menten and P . A . Morris}, year={2010} }