Herschel-HIFI observations of H2O, NH3 and N2H+ toward high-mass starless and proto-stellar clumps identified by the Hi-GAL survey
Journal
Date Issued
2015
Author(s)
Description
HIFI was designed and built by a consortium of institutes and university departments from across Europe, Canada, and the USA under the leadership of SRON Netherlands Institute for Space Research, Groningen, The Netherlands and with major contributions from Germany, France and the USA. Consortium members are: Canada: CSA, U.Waterloo; France: CESR, LAB, LERMA, IRAM; Germany: KOSMA, MPIfR, MPS; Ireland, NUI Maynooth; Italy: ASI, IAPS-INAF, Osservatorio Astrofisico di Arcetri-INAF; Netherlands: SRON, TUD; Poland: CAMK, CBK; Spain: Observatorio Astronomico Nacional (IGN), Centro de Astrobiologia (CSIC-INTA). Sweden: Chalmers University of Technology – MC2, RSS GARD; Onsala Space Observatory; Swedish National Space Board, Stockholm University – Stockholm Observatory; Switzerland: ETH Zurich, FHNW; USA: Caltech, JPL, NHSC. CMP acknowledges generous support from the Swedish National Space Board.
Abstract
Our present understanding of high-mass star formation still remains very
schematic. In particular, it is not yet clear how much of the difference
between low-mass and high-mass star formation occurs during the earliest star
formation phases. The chemical characteristics of massive cold clumps, and the
comparison with those of their low-mass counterparts, could provide crucial
clues about the exact role that chemistry plays in differentiating the early
phases of low-mass and high-mass star formation. Water, in particular, is a
unique probe of physical and chemical conditions in star-forming regions. Using
the HIFI instrument of Herschel we have observed the ortho-NH3 (1_0-0_0)
(572GHz), ortho-H2O (1_10-1_01) (557GHz) and N2H+ (6-5) (559GHz) lines toward a
sample of high-mass starless and proto-stellar clumps selected from the
"Herschel} Infrared Galactic Plane Survey" (Hi-GAL). We compare our results to
previous studies of low-mass and high-mass proto-stellar objects. At least one
of the three molecular lines was detected in 4 (out of 35) and 7 (out of 17)
objects in the l=59deg and l=30deg galactic regions, respectively. All detected
sources are proto-stellar. The water spectra are complex and consist of several
kinematic components, identified through a Gaussian decomposition, and in a few
sources inverse and regular P-Cygni profiles have been detected. All water line
profiles of the l=59deg region are dominated by a broad Gaussian emission
feature, indicating that the bulk of the water emission arises in outflows. No
such broad emission is detected toward the l=30deg objects. The ammonia line in
some cases also shows line wings and an inverse P-Cygni profile, thus
confirming that NH3 rotational transitions can be used to probe the dynamics of
high-mass star forming regions. Both bolometric and water line luminosity
increase with the continuum temperature.
Volume
583
Start page
A125
Issn Identifier
0004-6361
Ads BibCode
2015A&A...583A.125O
Rights
open.access
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