Nitrogen hydrides in interstellar gas. Herschel/HIFI observations towards G10.6-0.4 (W31C)
Perault, M.; Boulanger, F.; Falgarone, E.; Krełowski, J.; Godard, B.; Persson, C. M.; Martín-Pintado, J.; Morris, P.; Teyssier, D.; Planesas, P.; Lis, D. C.; Phillips, T. G.; Bell, T. A.; Cernicharo, J.; Encrenaz, P.; Gerin, M.; Goicoechea, J. R.; Goldsmith, P. F.; Gupta, H.; Herbst, E.; Joblin, C.; Neufeld, D. A.; Plume, R.; Schlemmer, S.; Stutzki, J.; Vastel, C.; Yu, S.; Schmidt, M.; Menten, K.; Sonnentrucker, P.; Lord, S.; Mookerjea, B.; Hennebelle, P.; Black, J. H.; Dartois, E.; Pearson, J.; Ravera, L.; Hily-Blant, P.; de Luca, M.; Geballe, T. R.; Gry, C.; Coutens, A.; Giesen, T.; Kołos, R.; Monje, R.; Salez, M.; Cais, P.; Kaźmierczak, M.; Cros, A.; Hassel, G. E.; Péron, I.; Gaufre, P.
Sweden, Spain, United States, France, Poland, India, Germany, Canada, Chile
Abstract
The HIFI instrument on board the Herschel Space Observatory has been used to observe interstellar nitrogen hydrides along the sight-line towards G10.6-0.4 in order to improve our understanding of the interstellar chemistry of nitrogen. We report observations of absorption in NH N = 1 ≤ftarrow 0, J = 2 ≤ftarrow 1 and ortho-NH2 11,1 ≥ts 00,0. We also observed ortho-NH3 10 ≥ts00, and 20 ≥ts 10, para-NH3 21 ≥ts 11, and searched unsuccessfully for NH+. All detections show emission and absorption associated directly with the hot-core source itself as well as absorption by foreground material over a wide range of velocities. All spectra show similar, non-saturated, absorption features, which we attribute to diffuse molecular gas. Total column densities over the velocity range 11-54 km s-1 are estimated. The similar profiles suggest fairly uniform abundances relative to hydrogen, approximately 6 × 10-9, 3 × 10-9, and 3 × 10-9 for NH, NH2, and NH3, respectively. These abundances are discussed with reference to models of gas-phase and surface chemistry.
Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA.Figures A.1 and A.2 (page 6) are only available in electronic form at http://www.aanda.org