Detection of hydrogen fluoride absorption in diffuse molecular clouds with Herschel/HIFI: an ubiquitous tracer of molecular gas
Artikel i vetenskaplig tidskrift, 2010
We discuss the detection of absorption by interstellar hydrogen fluoride (HF) along the sight line to the submillimeter continuum sources W49N and W51. We have used Herschel's HIFI instrument in dual beam switch mode to observe the 1232.4762 GHz J = 1-0 HF transition in the upper sideband of the band 5a receiver. We detected foreground absorption by HF toward both sources over a wide range of velocities. Optically thin absorption components were detected on both sight lines, allowing us to measure - as opposed to obtain a lower limit on - the column density of HF for the first time. As in previous observations of HF toward the source G10.6-0.4, the derived HF column density is typically comparable to that of water vapor, even though the elemental abundance of oxygen is greater than that of fluorine by four orders of magnitude. We used the rather uncertain N(CH) - N(H-2) relationship derived previously toward diffuse molecular clouds to infer the molecular hydrogen column density in the clouds exhibiting HF absorption. Within the uncertainties, we find that the abundance of HF with respect to H-2 is consistent with the theoretical prediction that HF is the main reservoir of gas-phase fluorine for these clouds. Thus, hydrogen fluoride has the potential to become an excellent tracer of molecular hydrogen, and provides a sensitive probe of clouds of small H-2 column density. Indeed, the observations of hydrogen fluoride reported here reveal the presence of a low column density diffuse molecular cloud along the W51 sight line, at an LSR velocity of similar to 24 km s(-1), that had not been identified in molecular absorption line studies prior to the launch of Herschel.
w49n
molecular processes
regions
h2o
w51
ISM: molecules
astronomy
astrochemistry
co
submillimeter: ISM
line-of-sight
abundance
Författare
P. Sonnentrucker
Johns Hopkins University
D. A. Neufeld
Johns Hopkins University
T. G. Phillips
California Institute of Technology (Caltech)
M. Gerin
LERMA - Laboratoire d'Etudes du Rayonnement et de la Matiere en Astrophysique et Atmospheres
D. C. Lis
California Institute of Technology (Caltech)
M. de Luca
LERMA - Laboratoire d'Etudes du Rayonnement et de la Matiere en Astrophysique et Atmospheres
J. R. Goicoechea
Centro de Astrobiologia (CAB)
John H Black
Chalmers, Rymd- och geovetenskap, Radioastronomi och astrofysik
T. A. Bell
California Institute of Technology (Caltech)
F. Boulanger
Institut d'Astrophysique Spatiale
J. Cernicharo
Centro de Astrobiologia (CAB)
A. Coutens
Université de Toulouse
E. Dartois
Institut d'Astrophysique Spatiale
M. Kazmierczak
Uniwersytet Mikolaja Kopernika
P. Encrenaz
LERMA - Laboratoire d'Etudes du Rayonnement et de la Matiere en Astrophysique et Atmospheres
E. Falgarone
LERMA - Laboratoire d'Etudes du Rayonnement et de la Matiere en Astrophysique et Atmospheres
T. R. Geballe
Gemini Observatory North
T. Giesen
Universität zu Köln
B. Godard
LERMA - Laboratoire d'Etudes du Rayonnement et de la Matiere en Astrophysique et Atmospheres
P. F. Goldsmith
California Institute of Technology (Caltech)
C. Gry
Laboratoire d'Astrophysique de Marseille
H. Gupta
California Institute of Technology (Caltech)
P. Hennebelle
LERMA - Laboratoire d'Etudes du Rayonnement et de la Matiere en Astrophysique et Atmospheres
E. Herbst
Ohio State University
P. Hily-Blant
Laboratoire d'Astrophysique de Grenoble
C. Joblin
Université de Toulouse
R. Kolos
Polish Academy of Sciences
J. Krelowski
Uniwersytet Mikolaja Kopernika
J. Martin-Pintado
Centro de Astrobiologia (CAB)
K. M. Menten
Max-Planck-Gesellschaft
Raquel Monje
California Institute of Technology (Caltech)
B. Mookerjea
Tata Institute of Fundamental Research
J. C. Pearson
California Institute of Technology (Caltech)
M. Perault
LERMA - Laboratoire d'Etudes du Rayonnement et de la Matiere en Astrophysique et Atmospheres
Carina Persson
Chalmers, Rymd- och geovetenskap, Radioastronomi och astrofysik
R. Plume
University of Calgary
M. Salez
LERMA - Laboratoire d'Etudes du Rayonnement et de la Matiere en Astrophysique et Atmospheres
S. Schlemmer
Universität zu Köln
M. Schmidt
Polish Academy of Sciences
J. Stutzki
Universität zu Köln
D. Teyssier
Europeiska rymdorganisationen (ESA)
C. Vastel
Université de Toulouse
S. Yu
California Institute of Technology (Caltech)
E. Caux
Université de Toulouse
R. Güsten
Max-Planck-Gesellschaft
W. A. Hatch
California Institute of Technology (Caltech)
T. Klein
Max-Planck-Gesellschaft
Imran Mehdi
California Institute of Technology (Caltech)
P. Morris
California Institute of Technology (Caltech)
J. S. Ward
California Institute of Technology (Caltech)
Astronomy and Astrophysics
0004-6361 (ISSN) 1432-0746 (eISSN)
Vol. 521 1 Article Number: L12- L12Ämneskategorier (SSIF 2011)
Astronomi, astrofysik och kosmologi
DOI
10.1051/0004-6361/201015082