The physical conditions in IRDC clumps from Herschel/HIFI observations of H2O

Shipman R. F., Van Der Tak F. F. S., Wyrowski F., Fabrice Herpin 1, 2, 3, 4, 5, 6 Frieswijk W.,
6 FORMATION STELLAIRE 2014
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. The earliest phases of high-mass star formation are poorly understood. Aims. Our goal is to determine the physical conditions and kinematic structure of massive starforming cloud clumps . Methods. We analyse H2O 557 GHz line profiles observed with HIFI toward four positions in two infrared-dark cloud clumps . By comparison with ground-based C17O, N2H+, CH3OH, and NH3 line observations, we constrain the volume density and kinetic temperature of the gas and estimate the column density and abundance of H2O and N2H+. Results. The observed water lines are complex with emission and absorption components. The absorption is redshifted and consistent with a cold envelope, while the emission is interpreted as resulting from protostellar outflows. The gas density in the clumps is ∼ 107 cm−3. The o-H2O outflow column density is 0.3 − 3.0 × 1014 cm−2. The o-H2O absorption column density is between 1.5 × 1014 and 2.6 × 1015 cm−2 with cold o-H2O abundances between 1.5 × 10−9 and 3.1 × 10−8. Conclusions. All clumps have high gas densities (∼ 107 cm−3) and display infalling gas. Three of the four clumps have outflows. The clumps form an evolutionary sequence as probed by H2O N2H+, NH3, and CH3OH. We find that G28-MM is the most evolved, followed by G11-MM and then G28-NH3. The least evolved clump is G11-NH3 which shows no signposts of starformation; G11-NH3 is a high-mass pre-stellar core.
Keywords : ISM Star Formation
Type de document :
Article dans une revue
Astronomy and Astrophysics - A&A, EDP Sciences, 2014, 570, pp.51. 〈10.1051/0004-6361/201423912〉
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https://hal.archives-ouvertes.fr/hal-01061817
Contributeur : Marie-Paule Pomies <>
Soumis le : lundi 8 septembre 2014 - 15:15:36
Dernière modification le : mercredi 27 juillet 2016 - 14:48:48

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Shipman R. F.,, Van Der Tak F. F. S.,, Wyrowski F.,, Fabrice Herpin, Frieswijk W.,. The physical conditions in IRDC clumps from Herschel/HIFI observations of H2O. Astronomy and Astrophysics - A&A, EDP Sciences, 2014, 570, pp.51. 〈10.1051/0004-6361/201423912〉. 〈hal-01061817〉

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