Herschel observations of EXtra-Ordinary Sources (HEXOS): Detection of hydrogen fluoride in absorption towards Orion KL
Menten, K. M.; Martin, P. G.; Murphy, J. A.; Maret, S.; Hartogh, P.; Ceccarelli, C.; Morris, P.; Schieder, R.; Ossenkopf, V.; Comito, C.; Schilke, P.; Lis, D. C.; Bergin, E. A.; Phillips, T. G.; Bell, T. A.; Crockett, N. R.; Wang, S.; Blake, G. A.; Caux, E.; Cernicharo, J.; Daniel, F.; Dubernet, M. -L.; Emprechtinger, M.; Encrenaz, P.; Gerin, M.; Giesen, T. F.; Goicoechea, J. R.; Goldsmith, P. F.; Herbst, E.; Joblin, C.; Johnstone, D.; Langer, W. D.; Latter, W. D.; Lord, S. D.; Melnick, G. J.; Müller, H. S. P.; Neufeld, D. A.; Pearson, J. C.; Pérault, M.; Plume, R.; Qin, S. -L.; Schlemmer, S.; Stutzki, J.; Trappe, N.; van der Tak, F. F. S.; Vastel, C.; Yorke, H. W.; Yu, S.; Güsten, R.; Boogert, A.; Kooi, J.; Zmuidzinas, J.; Honingh, N.; Karpov, A.; Krieg, J. -M.
United States, France, Spain, Germany, Canada, Ireland, Netherlands
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.
Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA.