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.

astrochemistry

ISM: molecules

absorption

submillimeter: ISM

cation

h-3(+)

model

laser magnetic-resonance

gas

star-forming regions

molecular processes

line

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

CalTech

D. C. Lis

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

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 Mikołaja Kopernika w Toruniu

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 Telescope

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 Mikołaja Kopernika w Toruniu

J. Martin-Pintado

Centro de Astrobiologia (CAB)

K. M. Menten

Max Planck-institutet

Raquel Monje

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 (ESA)

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

CalTech

Astronomy and Astrophysics

0004-6361 (ISSN) 1432-0746 (eISSN)

Vol. 521 1 Article Number: L10- L10

Ämneskategorier

Astronomi, astrofysik och kosmologi

DOI

10.1051/0004-6361/201015077

Mer information

Senast uppdaterat

2018-11-05