Herschel/HIFI observations of spectrally resolved methylidyne signatures toward the high-mass star-forming core NGC 6334I

M. H. D. Van Der Wiel F. F. S. Van Der Tak 1, 2 D. C. Lis 3 T. Bell 4 E. A. Bergin 5 C. Comito 6 M. Emprechtinger 7 P. Schilke 6, 8 E. Caux 9, 10 C. Ceccarelli 4 Alain Baudry 11 P. F. Goldsmith E. Herbst 12, 13 W. Langer 4 S. Lord 4 D. Neufeld 4 Justin Pearson 4 T. Phillips 4 R. Rolffs 14, 15 H. Yorke 4 A. Bacmann 11 M. Benedettini 4 G. A. Blake 16 A. Boogert 4 S. Bottinelli 17 S. Cabrit 18 P. Caselli 19 Alain Castets 4 J. Cernicharo 20 C. Codella 4 A. Coutens 4 N. Crimier 4 K. Demyk 4 C. Dominik 21 P. Encrenaz 18 E. Falgarone 22 A. Fuente 4 M. Gerin 18, 22 F. Helmich 4 P. Hennebelle 4 T. Henning 23 P. Hily-Blant 4 T. Jacq 11 C. Kahane 4 M. Kama 4 A. Klotz 17, 24 B. Lefloch 4 A. Lorenzani 19 S. Maret 4 G. Melnick 4 B. Nisini 25 S. Pacheco 4 L. Pagani 18 B. Parise 17, 26 M. Salez 4 P. Saraceno 27 K. Schuster 4 A. G. G. M. Tielens 2 C. Vastel 9, 10 S. Viti 4 Valentine Wakelam 28 A. Walters 4 F. Wyrowski 29 K. Edwards J. Zmuidzinas 7 P. Morris 30 L. A. Samoska D. Teyssier
11 FORMATION STELLAIRE 2010
L3AB - Laboratoire d'astrodynamique, d'astrophysique et d'aéronomie de bordeaux, OASU - Observatoire aquitain des sciences de l'univers, LAB - Laboratoire d'Astrophysique de Bordeaux [Pessac], Université Sciences et Technologies - Bordeaux 1
28 AMOR 2010
L3AB - Laboratoire d'astrodynamique, d'astrophysique et d'aéronomie de bordeaux, OASU - Observatoire aquitain des sciences de l'univers, LAB - Laboratoire d'Astrophysique de Bordeaux [Pessac], Université Sciences et Technologies - Bordeaux 1
Abstract : Context. In contrast to the more extensively studied dense star-forming cores, little is known about diffuse gas surrounding star-forming regions. Aims: We study the molecular gas in the Galactic high-mass star-forming region NGC 6334I, which contains diffuse, quiescent components that are inconspicuous in widely used molecular tracers such as CO. Methods: We present Herschel/HIFI observations of methylidyne (CH) toward NGC 6334I observed as part of the "Chemical HErschel Survey of Star forming regions" (CHESS) key program. HIFI resolves each of the six hyperfine components of the lowest rotational transition (J = 3/2 - 1/2) of CH, observed in both emission and absorption. Results: The CH emission features appear close to the systemic velocity of NGC 6334I, while its measured FWHM linewidth of 3 km s-1 is smaller than previously observed in dense gas tracers such as NH3 and SiO. The CH abundance in the hot core is ~7 × 10-11, two to three orders of magnitude lower than in diffuse clouds. While other studies find distinct outflows in, e.g., CO and H2O toward NGC 6334I, we do not detect any outflow signatures in CH. At least two redshifted components of cold absorbing material must be present at -3.0 and +6.5 km s-1 to explain the absorption signatures. We derive a CH column density (NCH) of 7 × 1013 and 3 × 1013 cm-2 for these two absorbing clouds. We find evidence of two additional absorbing clouds at +8.0 and 0.0 km s-1, both with NCH ≈ 2 × 1013 cm-2. Turbulent linewidths for the four absorption components vary between 1.5 and 5.0 km s-1 in FWHM. We constrain the physical properties and locations of the clouds by matching our CH absorbers with the absorption signatures seen in other molecular tracers. Conclusions: In the hot core, molecules such as H2O and CO trace gas that is heated and dynamically influenced by outflow activity, whereas the CH molecule traces more quiescent material. The four CH absorbing clouds have column densities and turbulent properties that are consistent with those of diffuse clouds: two are located in the direct surroundings of NGC 6334, and two are unrelated foreground clouds. Local density and dynamical effects influence the chemical composition of the physical components of NGC 6334, which causes some components to be seen in CH but not in other tracers, and vice versa. Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA.Acknowledgements (page 5) are only available in electronic form at http://www.aanda.org
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https://hal.archives-ouvertes.fr/hal-00633400
Contributeur : Laurent Pagani <>
Soumis le : mardi 18 octobre 2011 - 14:28:47
Dernière modification le : mercredi 27 septembre 2017 - 01:21:51

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M. H. D. Van Der Wiel, F. F. S. Van Der Tak, D. C. Lis, T. Bell, E. A. Bergin, et al.. Herschel/HIFI observations of spectrally resolved methylidyne signatures toward the high-mass star-forming core NGC 6334I. Astronomy and Astrophysics - A&A, EDP Sciences, 2010, 521, pp.L43. 〈10.1051/0004-6361/201015096〉. 〈hal-00633400〉

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