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Herschel observations of the hydroxyl radical (OH) in young stellar objects

Wampfler, S. F. and Blake, G. A. and Lis, D. (2010) Herschel observations of the hydroxyl radical (OH) in young stellar objects. Astronomy and Astrophysics, 521 . Art. No. L36. ISSN 0004-6361.

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Aims. “Water In Star-forming regions with Herschel” (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 ≳ 250 K) chemistry connects OH and H_2O through the OH + H_2 ⇔ 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 + _(γUV) ⇒ 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 ≳ 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.

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Blake, G. A.0000-0003-0787-1610
Lis, D.0000-0002-0500-4700
Additional Information:© 2010 ESO. Received 31 May 2010, Accepted 12 July 2010, Published online 01 October 2010. Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA. Appendices (page 6) are only available in electronic form at The work on star formation at ETH Zurich is partially funded by the Swiss National Science Foundation (grant nr. 200020-113556). This program is made possible thanks to the Swiss HIFI guaranteed time program. HIFI has been designed and built by a consortium of institutes and university departments from across Europe, Canada and the United States under the leadership of SRON Netherlands Institute for Space Research, Groningen, The Netherlands and with major contributions from Germany, France and the US. Consortium members are: Canada: CSA, U. Waterloo; France: CESR, LAB, LERMA, IRAM; Germany: KOSMA, MPIfR, MPS; Ireland, NUI Maynooth; Italy: ASI, IFSI-INAF, Osservatorio Astrofisico di Arcetri-INAF; Netherlands: SRON, TUD; Poland: CAMK, CBK; Spain: Observatorio Astronmico Nacional (IGN), Centro de Astrobiologa (CSIC-INTA). Sweden: Chalmers University of Technology – MC2, RSS & GARD; Onsala Space Observatory; Swedish National Space Board, Stockholm University – Stockholm Observatory; Switzerland: ETH Zurich, FHNW; USA: Caltech, JPL, NHSC.
Funding AgencyGrant Number
Swiss National Science Foundation (SNSF)200020-113556
Subject Keywords:astrochemistry – stars: formation – ISM: molecules – ISM: jets and outflows – ISM: individual objects: HH 46
Record Number:CaltechAUTHORS:20110106-151329692
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Official Citation:Herschel observations of the hydroxyl radical (OH) in young stellar objects S. F. Wampfler, G. J. Herczeg, S. Bruderer, A. O. Benz, E. F. van Dishoeck, L. E. Kristensen, R. Visser, S. D. Doty, M. Melchior, T. A. van Kempen, U. A. Yıldız, C. Dedes, J. R. Goicoechea, A. Baudry, G. Melnick, R. Bachiller, M. Benedettini, E. Bergin, P. Bjerkeli, G. A. Blake, S. Bontemps, J. Braine, P. Caselli, J. Cernicharo, C. Codella, F. Daniel, A. M. di Giorgio, C. Dominik, P. Encrenaz, M. Fich, A. Fuente, T. Giannini, Th. de Graauw, F. Helmich, F. Herpin, M. R. Hogerheijde, T. Jacq, D. Johnstone, J. K. Jørgensen, B. Larsson, D. Lis, R. Liseau, M. Marseille, C. Mc Coey, D. Neufeld, B. Nisini, M. Olberg, B. Parise, J. C. Pearson, R. Plume, C. Risacher, J. Santiago-García, P. Saraceno, R. Shipman, M. Tafalla, F. F. S. van der Tak, F. Wyrowski, P. Roelfsema, W. Jellema, P. Dieleman, E. Caux and J. Stutzki A&A 521 L36 (2010) DOI: 10.1051/0004-6361/201015112
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:21636
Deposited By: Benjamin Perez
Deposited On:06 Jan 2011 23:29
Last Modified:03 Oct 2019 02:27

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