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.
ISM: individual objects: HH 46
astrochemistry
stars: formation
ISM: molecules
ISM: jets and outflows
Författare
S. F. Wampfler
Eidgenössische Technische Hochschule Zürich (ETH)
G. J. Herczeg
Max-Planck-Gesellschaft
S. Bruderer
Eidgenössische Technische Hochschule Zürich (ETH)
A. O. Benz
Eidgenössische Technische Hochschule Zürich (ETH)
E. F. van Dishoeck
Universiteit Leiden
Max-Planck-Gesellschaft
L. Kristensen
Universiteit Leiden
R. Visser
Universiteit Leiden
S. Doty
Denison University
M. Melchior
Eidgenössische Technische Hochschule Zürich (ETH)
Fachhochschule Nordwestschweiz
T. A. van Kempen
Harvard-Smithsonian Center for Astrophysics
U. A. Yildiz
Universiteit Leiden
C. Dedes
Eidgenössische Technische Hochschule Zürich (ETH)
J. R. Goicoechea
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 Astronómico Nacional (OAN)
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
California Institute of Technology (Caltech)
S. Bontemps
Laboratoire d'Astrophysique de Bordeaux
Institut National des Sciences de l'Univers
J. Braine
Institut National des Sciences de l'Univers
Laboratoire d'Astrophysique de Bordeaux
P. Caselli
Osservatorio Astrofisico di Arcetri
University of Leeds
J. Cernicharo
Centro de Astrobiologia (CAB)
C. Codella
Osservatorio Astrofisico di Arcetri
F. Daniel
Centro de Astrobiologia (CAB)
A. M. di Giorgio
Universita degli Studi di Roma Tor Vergata
C. Dominik
Radboud Universiteit
Anton Pannekoek Institute for Astronomy
P. Encrenaz
LERMA - Laboratoire d'Etudes du Rayonnement et de la Matiere en Astrophysique et Atmospheres
M. Fich
University of Waterloo
A. Fuente
Observatorio Astronómico Nacional (OAN)
T. Giannini
Osservatorio Astronomico di Roma
T. de Graauw
Netherlands Institute for Space Research (SRON)
F. Helmich
Netherlands Institute for Space Research (SRON)
F. Herpin
Institut National des Sciences de l'Univers
Laboratoire d'Astrophysique de Bordeaux
M. R. Hogerheijde
Universiteit Leiden
T. Jacq
Institut National des Sciences de l'Univers
Laboratoire d'Astrophysique de Bordeaux
D. Johnstone
National Research Council Canada
University of Victoria
J. K. Jorgensen
Köpenhamns universitet
B. Larsson
Stockholms universitet
D. Lis
California Institute of Technology (Caltech)
René Liseau
Chalmers, Institutionen för radio- och rymdvetenskap, Radioastronomi och astrofysik
M. Marseille
Netherlands Institute for Space Research (SRON)
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-Gesellschaft
J. C. Pearson
Jet Propulsion Laboratory, California Institute of Technology
R. Plume
University of Calgary
C. Risacher
Netherlands Institute for Space Research (SRON)
J. Santiago-García
Institut de Radioastronomie Millimétrique (IRAM)
P. Saraceno
Universita degli Studi di Roma Tor Vergata
R. Shipman
Netherlands Institute for Space Research (SRON)
M. Tafalla
Observatorio Astronómico Nacional (OAN)
F. F. S. van der Tak
Netherlands Institute for Space Research (SRON)
Rijksuniversiteit Groningen
F. Wyrowski
Max-Planck-Gesellschaft
P. Roelfsema
Netherlands Institute for Space Research (SRON)
W. Jellema
Netherlands Institute for Space Research (SRON)
P. Dieleman
Netherlands Institute for Space Research (SRON)
E. Caux
Université 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 1 Art. Nr. L36- L36Ämneskategorier (SSIF 2011)
Astronomi, astrofysik och kosmologi
Fundament
Grundläggande vetenskaper
DOI
10.1051/0004-6361/201015112