Nitrogen hydrides in interstellar gas. Herschel/HIFI observations towards G10.6-0.4 (W31C)
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- Publication:
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Astronomy and Astrophysics
- Pub Date:
- October 2010
- DOI:
- 10.1051/0004-6361/201015105
- arXiv:
- arXiv:1007.2550
- Bibcode:
- 2010A&A...521L..45P
- Keywords:
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- astrochemistry;
- ISM: abundances;
- ISM: molecules;
- molecular processes;
- submillimetre: ISM;
- line: formation;
- Astrophysics - Astrophysics of Galaxies
- E-Print:
- 5 pages, 3 figures, 2 online pages with 2 figures. Accepted for publication in A&