Herschel/HIFI measurements of the ortho/para ratio in water towards Sagittarius B2(M) and W31C - Archive ouverte HAL Access content directly
Journal Articles Astronomy and Astrophysics - A&A Year : 2010

Herschel/HIFI measurements of the ortho/para ratio in water towards Sagittarius B2(M) and W31C

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D. C. Lis
  • Function : Author
T. G. Phillips
  • Function : Author
P. F. Goldsmith
  • Function : Author
D. A. Neufeld
  • Function : Author
E. Herbst
  • Function : Author
C. Comito
  • Function : Author
P. Schilke
H. S. P. Müller
  • Function : Author
E. A. Bergin
  • Function : Author
M. Gerin
  • Function : Author
T. A. Bell
  • Function : Author
M. Emprechtinger
  • Function : Author
J. H. Black
  • Function : Author
G. A. Blake
  • Function : Author
F. Boulanger
  • Function : Author
J. Cernicharo
A. Coutens
N. R. Crockett
  • Function : Author
F. Daniel
  • Function : Author
E. Dartois
  • Function : Author
M. de Luca
  • Function : Author
P. Encrenaz
  • Function : Author
E. Falgarone
  • Function : Author
T. R. Geballe
  • Function : Author
B. Godard
  • Function : Author
T. F. Giesen
  • Function : Author
J. R. Goicoechea
  • Function : Author
C. Gry
H. Gupta
  • Function : Author
P. Hennebelle
  • Function : Author
R. Kołos
  • Function : Author
J. Krełowski
  • Function : Author
D. Johnstone
  • Function : Author
M. Kaźmierczak
  • Function : Author
S. D. Lord
  • Function : Author
P. G. Martin
  • Function : Author
J. Martín-Pintado
  • Function : Author
G. J. Melnick
  • Function : Author
K. M. Menten
  • Function : Author
R. Monje
  • Function : Author
B. Mookerjea
  • Function : Author
P. Morris
J. A. Murphy
  • Function : Author
V. Ossenkopf
  • Function : Author
J. C. Pearson
  • Function : Author
M. Pérault
  • Function : Author
C. Persson
  • Function : Author
R. Plume
  • Function : Author
S. -L. Qin
  • Function : Author
M. Salez
  • Function : Author
S. Schlemmer
  • Function : Author
M. Schmidt
  • Function : Author
P. Sonnentrucker
  • Function : Author
J. Stutzki
  • Function : Author
D. Teyssier
N. Trappe
  • Function : Author
F. F. S. van Der Tak
  • Function : Author
S. Wang
  • Function : Author
H. W. Yorke
  • Function : Author
S. Yu
  • Function : Author
J. Zmuidzinas
  • Function : Author
A. Boogert
  • Function : Author
N. Erickson
  • Function : Author
A. Karpov
  • Function : Author
J. Kooi
  • Function : Author
F. W. Maiwald
  • Function : Author
R. Schieder
  • Function : Author
P. Zaal
  • Function : Author

Abstract

We present Herschel/HIFI observations of the fundamental rotational transitions of ortho- and para-H_216O and H_218O in absorption towards Sagittarius B2(M) and W31C. The ortho/para ratio in water in the foreground clouds on the line of sight towards these bright continuum sources is generally consistent with the statistical high-temperature ratio of 3, within the observational uncertainties. However, somewhat unexpectedly, we derive a low ortho/para ratio of 2.35 ± 0.35, corresponding to a spin temperature of ~27 K, towards Sagittarius B2(M) at velocities of the expanding molecular ring. Water molecules in this region appear to have formed with, or relaxed to, an ortho/para ratio close to the value corresponding to the local temperature of the gas and dust.

Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA.

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Dates and versions

insu-03625635 , version 1 (31-03-2022)

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Attribution - CC BY 4.0

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D. C. Lis, T. G. Phillips, P. F. Goldsmith, D. A. Neufeld, E. Herbst, et al.. Herschel/HIFI measurements of the ortho/para ratio in water towards Sagittarius B2(M) and W31C. Astronomy and Astrophysics - A&A, 2010, 521, pp.L26+. ⟨10.1051/0004-6361/201015072⟩. ⟨insu-03625635⟩
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