Detection of hydrogen fluoride absorption in diffuse molecular clouds with Herschel/HIFI: an ubiquitous tracer of molecular gas
Journal article, 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.

regions

ISM: molecules

line-of-sight

h2o

w51

astrochemistry

co

astronomy

abundance

w49n

submillimeter: ISM

molecular processes

Author

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, Earth and Space Sciences, Radio Astronomy and Astrophysics

T. A. Bell

California Institute of Technology (Caltech)

F. Boulanger

Institut d'Astrophysique Spatiale

J. Cernicharo

Centro de Astrobiologia (CAB)

A. Coutens

University of 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

University of Cologne

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

E. Herbst

Ohio State University

P. Hily-Blant

Laboratoire d'Astrophysique de Grenoble

C. Joblin

University of 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 Society

Raquel Monje

California Institute of Technology (Caltech)

B. Mookerjea

Tata Institute of Fundamental Research

J. C. Pearson

Jet Propulsion Laboratory, California Institute of Technology

M. Perault

LERMA - Laboratoire d'Etudes du Rayonnement et de la Matiere en Astrophysique et Atmospheres

Carina Persson

Chalmers, Earth and Space Sciences, Radio Astronomy and Astrophysics

R. Plume

University of Calgary

M. Salez

LERMA - Laboratoire d'Etudes du Rayonnement et de la Matiere en Astrophysique et Atmospheres

S. Schlemmer

University of Cologne

M. Schmidt

Polish Academy of Sciences

J. Stutzki

University of Cologne

D. Teyssier

European Space Astronomy Centre (ESAC)

C. Vastel

University of Toulouse

S. Yu

Jet Propulsion Laboratory, California Institute of Technology

E. Caux

University of Toulouse

R. Güsten

Max Planck Society

W. A. Hatch

Jet Propulsion Laboratory, California Institute of Technology

T. Klein

Max Planck Society

Imran Mehdi

Jet Propulsion Laboratory, California Institute of Technology

P. Morris

California Institute of Technology (Caltech)

J. S. Ward

Jet Propulsion Laboratory, California Institute of Technology

Astronomy and Astrophysics

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

Vol. 521 1 Article Number: L12- L12

Subject Categories

Astronomy, Astrophysics and Cosmology

DOI

10.1051/0004-6361/201015082

More information

Latest update

11/5/2018