The physical conditions in IRDC clumps from Herschel/HIFI observations of H2O - Archive ouverte HAL Accéder directement au contenu
Article Dans Une Revue Astronomy and Astrophysics - A&A Année : 2014

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

Résumé

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.

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Dates et versions

hal-01061817 , version 1 (08-09-2014)

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Citer

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, 2014, 570, pp.51. ⟨10.1051/0004-6361/201423912⟩. ⟨hal-01061817⟩

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