The physical conditions in IRDC clumps from Herschel/HIFI observations of H2O
HERPIN, Fabrice
Université de Bordeaux [UB]
Laboratoire d'Astrophysique de Bordeaux [Pessac] [LAB]
Laboratoire d'astrodynamique, d'astrophysique et d'aéronomie de bordeaux [L3AB]
Observatoire aquitain des sciences de l'univers [OASU]
Université Sciences et Technologies - Bordeaux 1 [UB]
FORMATION STELLAIRE 2014
< Reduce
Université de Bordeaux [UB]
Laboratoire d'Astrophysique de Bordeaux [Pessac] [LAB]
Laboratoire d'astrodynamique, d'astrophysique et d'aéronomie de bordeaux [L3AB]
Observatoire aquitain des sciences de l'univers [OASU]
Université Sciences et Technologies - Bordeaux 1 [UB]
FORMATION STELLAIRE 2014
Language
en
Article de revue
This item was published in
Astronomy and Astrophysics - A&A. 2014-10, vol. 570, p. 51
EDP Sciences
English 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 ...Read more >
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.Read less <
English Keywords
ISM
Star Formation
Origin
Hal imported