Herschel/HIFI observations of interstellar OH+ and H2O+ towards W49N: a probe of diffuse clouds with a small molecular fraction
Artikel i vetenskaplig tidskrift, 2010
We report the detection of absorption by interstellar hydroxyl cations and water cations, along the sight-line to the bright continuum source W49N. We have used Herschel's HIFI instrument, in dual beam switch mode, to observe the 972 GHz N = 1-0 transition of OH+ and the 1115 GHz 1(11)-0(00) transition of ortho-H2O+. The resultant spectra show absorption by ortho-H2O+, and strong absorption by OH+, in foreground material at velocities in the range 0 to 70 km s(-1) with respect to the local standard of rest. The inferred OH+/H2O+ abundance ratio ranges from similar to 3 to similar to 15, implying that the observed OH+ arises in clouds of small molecular fraction, in the 2-8% range. This conclusion is confirmed by the distribution of OH+ and H2O+ in Doppler velocity space, which is similar to that of atomic hydrogen, as observed by means of 21 cm absorption measurements, and dissimilar from that typical of other molecular tracers. The observed OH+/H abundance ratio of a few x10(-8) suggests a cosmic ray ionization rate for atomic hydrogen of 0.6-2.4 x 10(-16) s(-1), in good agreement with estimates inferred previously for diffuse clouds in the Galactic disk from observations of interstellar H-3(+) and other species.
model
line
astrochemistry
laser magnetic-resonance
cation
gas
star-forming regions
ISM: molecules
submillimeter: ISM
h-3(+)
molecular processes
absorption
Författare
D. A. Neufeld
Johns Hopkins University
J. R. Goicoechea
Centro de Astrobiologia (CAB)
P. Sonnentrucker
Johns Hopkins University
John H Black
Chalmers, Rymd- och geovetenskap, Radioastronomi och astrofysik
J. C. Pearson
Jet Propulsion Laboratory, California Institute of Technology
S. Yu
Jet Propulsion Laboratory, California Institute of Technology
T. G. Phillips
California Institute of Technology (Caltech)
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
E. Herbst
Ohio State University
P. B. Rimmer
Ohio State University
M. Gerin
LERMA - Laboratoire d'Etudes du Rayonnement et de la Matiere en Astrophysique et Atmospheres
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
Jet Propulsion Laboratory, California Institute of Technology
C. Gry
Laboratoire d'Astrophysique de Marseille
H. Gupta
Jet Propulsion Laboratory, California Institute of Technology
P. Hennebelle
LERMA - Laboratoire d'Etudes du Rayonnement et de la Matiere en Astrophysique et Atmospheres
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
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
European Space Astronomy Centre (ESAC)
C. Vastel
Université de Toulouse
A. Cros
Université de Toulouse
K. Klein
University of Waterloo
A. Lorenzani
Osservatorio Astrofisico di Arcetri
S. Philipp
Deutsches Zentrums für Luft- und Raumfahrt (DLR)
A. Samoska
Jet Propulsion Laboratory, California Institute of Technology
R. Shipman
Netherlands Institute for Space Research (SRON)
Aggm Tielens
Universiteit Leiden
R. Szczerba
Polish Academy of Sciences
J. Zmuidzinas
California Institute of Technology (Caltech)
Astronomy and Astrophysics
0004-6361 (ISSN) 1432-0746 (eISSN)
Vol. 521 1 Article Number: L10- L10Ämneskategorier
Astronomi, astrofysik och kosmologi
DOI
10.1051/0004-6361/201015077