Herschel observations of the hydroxyl radical (OH) in young stellar objects
Artikel i vetenskaplig tidskrift, 2010

Aims: \ldquoWater In Star-forming regions with Herschel\rdquo (WISH) is a Herschel key program investigating the water chemistry in young stellar objects (YSOs) during protostellar evolution. Hydroxyl (OH) is one of the reactants in the chemical network most closely linked to the formation and destruction of H_2O. High-temperature (T \gap 250 K) chemistry connects OH and H_2O through the OH + H_2 Leftrightarrow H_2O + H reactions. Formation of H_2O from OH is efficient in the high-temperature regime found in shocks and the innermost part of protostellar envelopes. Moreover, in the presence of UV photons, OH can be produced from the photo-dissociation of H_2O through H_2O + γ_UV Rightarrow OH + H. Methods: High-resolution spectroscopy of the 163.12 µm triplet of OH towards HH 46 and NGC 1333 IRAS 2A was carried out with the Heterodyne Instrument for the Far Infrared (HIFI) on board the Herschel Space Observatory. The low- and intermediate-mass protostars HH 46, TMR 1, IRAS 15398-3359, DK Cha, NGC 7129 FIRS 2, and NGC 1333 IRAS 2A were observed with the Photodetector Array Camera and Spectrometer (PACS) on Herschel in four transitions of OH and two [O i] lines. Results: The OH transitions at 79, 84, 119, and 163 µm and [O i] emission at 63 and 145 µm were detected with PACS towards the class I low-mass YSOs as well as the intermediate-mass and class I Herbig Ae sources. No OH emission was detected from the class 0 YSO NGC 1333 IRAS 2A, though the 119 µm was detected in absorption. With HIFI, the 163.12 µm was not detected from HH 46 and only tentatively detected from NGC 1333 IRAS 2A. The combination of the PACS and HIFI results for HH 46 constrains the line width (FWHM \gap 11 km s^-1) and indicates that the OH emission likely originates from shocked gas. This scenario is supported by trends of the OH flux increasing with the [O i] flux and the bolometric luminosity, as found in our sample. Similar OH line ratios for most sources suggest that OH has comparable excitation temperatures despite the different physical properties of the sources.

stars: formation

astrochemistry

ISM: individual objects: HH 46

ISM: molecules

ISM: jets and outflows

Författare

S. F. Wampfler

Eidgenössische Technische Hochschule Zürich (ETH)

G. J. Herczeg

Max Planck-institutet

S. Bruderer

Eidgenössische Technische Hochschule Zürich (ETH)

A. O. Benz

Eidgenössische Technische Hochschule Zürich (ETH)

E. F. van Dishoeck

Leiden University

Max Planck-institutet

L. Kristensen

Leiden University

R. Visser

Leiden University

S. Doty

Denison University

M. Melchior

Eidgenössische Technische Hochschule Zürich (ETH)

University of Applied Sciences Northwestern Switzerland, School of Enginnering

T. A. van Kempen

Harvard-Smithsonian Center for Astrophysics

U. A. Yildiz

Leiden University

C. Dedes

Eidgenössische Technische Hochschule Zürich (ETH)

J. R. Goicoechea

CSIC-INTA - Centro de Astrobiologia (CAB)

A. Baudry

Institut National des Sciences de l'Univers

Laboratoire d'Astrophysique de Bordeaux

G. J. Melnick

Harvard-Smithsonian Center for Astrophysics

R. Bachiller

Observatorio Astronomico Nacional

M. Benedettini

Universita degli Studi di Roma Tor Vergata

E. A. Bergin

University of Michigan

Per Bjerkeli

Chalmers, Rymd- och geovetenskap, Onsala rymdobservatorium

G. A. Blake

Caltech Division of Geological and Planetary Sciences

S. Bontemps

Laboratoire d'Astrophysique de Bordeaux

Institut National des Sciences de l'Univers

J. Braine

Laboratoire d'Astrophysique de Bordeaux

Institut National des Sciences de l'Univers

P. Caselli

Osservatorio Astrofisico di Arcetri

University of Leeds

J. Cernicharo

CSIC-INTA - Centro de Astrobiologia (CAB)

C. Codella

Osservatorio Astrofisico di Arcetri

F. Daniel

CSIC-INTA - Centro de Astrobiologia (CAB)

A. M. di Giorgio

Universita degli Studi di Roma Tor Vergata

C. Dominik

Astronomical Institute Anton Pannekoek

Radboud Universiteit

P. Encrenaz

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

M. Fich

University of Waterloo

A. Fuente

Observatorio Astronomico Nacional

T. Giannini

Osservatorio Astronomico di Roma

T. de Graauw

SRON Netherlands Institute for Space Research

F. Helmich

SRON Netherlands Institute for Space Research

F. Herpin

Laboratoire d'Astrophysique de Bordeaux

Institut National des Sciences de l'Univers

M. R. Hogerheijde

Leiden University

T. Jacq

Laboratoire d'Astrophysique de Bordeaux

Institut National des Sciences de l'Univers

D. Johnstone

National Research Council Canada

University of Victoria

J. K. Jorgensen

Kobenhavns Universitet

B. Larsson

Stockholms universitet

D. Lis

CalTech

René Liseau

Chalmers, Institutionen för radio- och rymdvetenskap, Radioastronomi och astrofysik

M. Marseille

SRON Netherlands Institute for Space Research

C. McCoey

University of Waterloo

Western University

D. A. Neufeld

Johns Hopkins University

B. Nisini

Osservatorio Astronomico di Roma

Michael Olberg

Chalmers, Institutionen för radio- och rymdvetenskap, Radioastronomi och astrofysik

B. Parise

Max Planck-institutet

J. C. Pearson

Jet Propulsion Laboratory, California Institute of Technology

R. Plume

University of Calgary

C. Risacher

SRON Netherlands Institute for Space Research

J. Santiago-García

Instituto de Radioastronomia Milimetrica

P. Saraceno

Universita degli Studi di Roma Tor Vergata

R. Shipman

SRON Netherlands Institute for Space Research

M. Tafalla

Observatorio Astronomico Nacional

F. F. S. van der Tak

SRON Netherlands Institute for Space Research

University of Groningen, Kapteyn Astronomical Institute

F. Wyrowski

Max Planck-institutet

P. Roelfsema

SRON Netherlands Institute for Space Research

W. Jellema

SRON Netherlands Institute for Space Research

P. Dieleman

SRON Netherlands Institute for Space Research

E. Caux

Universite de Toulouse

Institut National des Sciences de l'Univers

J. Stutzki

Universität zu Köln

Astronomy and Astrophysics

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

Vol. 521 Art. Nr. L36- L36

Ämneskategorier

Astronomi, astrofysik och kosmologi

Fundament

Grundläggande vetenskaper

DOI

10.1051/0004-6361/201015112