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Deep observations of O_2 toward a low-mass protostar with Herschel-HIFI

Yildiz, Umut A. and Acharyya, Kinsuk and Goldsmith, Paul F. and van Dishoeck, Ewine F. and Melnick, Gary and Snell, Ronald and Liseau, René and Chen, Jo-Hsin and Pagani, Laurent and Bergin, Edwin and Caselli, Paola and Herbst, Eric and Kristensen, Lars E. and Visser, Ruud and Lis, Dariusz C. and Gerin, Maryvonne (2013) Deep observations of O_2 toward a low-mass protostar with Herschel-HIFI. Astronomy and Astrophysics, 558 . Art. No. A58. ISSN 0004-6361. http://resolver.caltech.edu/CaltechAUTHORS:20140108-133159430

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Abstract

Context. According to traditional gas-phase chemical models, O_2 should be abundant in molecular clouds, but until recently, attempts to detect interstellar O_2 line emission with ground- and space-based observatories have failed. Aims. Following the multi-line detections of O_2 with low abundances in the Orion and ρ Oph A molecular clouds with Herschel, it is important to investigate other environments, and we here quantify the O_2 abundance near a solar-mass protostar. Methods. Observations of molecular oxygen, O_2, at 487 GHz toward a deeply embedded low-mass Class 0 protostar, NGC 1333-IRAS 4A, are presented, using the Heterodyne Instrument for the Far Infrared (HIFI) on the Herschel Space Observatory. Complementary data of the chemically related NO and CO molecules are obtained as well. The high spectral resolution data are analysed using radiative transfer models to infer column densities and abundances, and are tested directly against full gas-grain chemical models. Results. The deep HIFI spectrum fails to show O_2 at the velocity of the dense protostellar envelope, implying one of the lowest abundance upper limits of O_2/H_2 at ≤6 × 10^(-9) (3σ). The O_2/CO abundance ratio is less than 0.005. However, a tentative (4.5σ) detection of O_2 is seen at the velocity of the surrounding NGC 1333 molecular cloud, shifted by 1 km s^(-1) relative to the protostar. For the protostellar envelope, pure gas-phase models and gas-grain chemical models require a long pre-collapse phase (~0.7–1 × 10^6 years), during which atomic and molecular oxygen are frozen out onto dust grains and fully converted to H_2O, to avoid overproduction of O_2 in the dense envelope. The same model also reproduces the limits on the chemically related NO molecule if hydrogenation of NO on the grains to more complex molecules such as NH_2OH, found in recent laboratory experiments, is included. The tentative detection of O_2 in the surrounding cloud is consistent with a low-density PDR model with small changes in reaction rates. Conclusions. The low O_2 abundance in the collapsing envelope around a low-mass protostar suggests that the gas and ice entering protoplanetary disks is very poor in O_2.


Item Type:Article
Related URLs:
URLURL TypeDescription
http://www.aanda.org/articles/aa/abs/2013/10/aa21944-13/aa21944-13.htmlPublisherArticle
http://dx.doi.org/10.1051/0004-6361/201321944DOIArticle
http://arxiv.org/abs/1307.8031arXivDiscussion Paper
ORCID:
AuthorORCID
van Dishoeck, Ewine F.0000-0001-7591-1907
Lis, Dariusz C.0000-0002-0500-4700
Additional Information:© 2013 ESO. Article published by EDP Sciences. Received 22 May 2013. Accepted 26 July 2013. Published online 03 October 2013. Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA. U.A.Y. and astrochemistry in Leiden are supported by the Netherlands Research School for Astronomy (NOVA), by a Spinoza grant and grant 614.001.008 from the Netherlands Organisation for Scientific Research (NWO), and by the European Community’s Seventh Framework Programme FP7/2007–2013 under grant agreement 238258 (LASSIE) and 291141 (CHEMPLAN). This work was carried out in part at the Jet Propulsion Laboratory, which is operated by the California Institute of Technology under contract with NASA. The authors are grateful to many funding agencies and the HIFI-ICC staff, who has been contributing for the construction of Herschel and HIFI for many years. 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 Astronómico Nacional (IGN), Centro de Astrobiología (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, NASA/JPL, NHSC.
Funders:
Funding AgencyGrant Number
Nederlandse Onderzoekschool voor de Astronomie (NOVA)UNSPECIFIED
Nederlandse Organisatie voor Wetenschappelijk Onderzoek (NWO)614.001.008
European Research Council (ERC)238258 (LASSIE)
European Research Council (ERC)291141 (CHEMPLAN)
NASA/JPL/CaltechUNSPECIFIED
Subject Keywords:astrochemistry, stars: formation, ISM: molecules, ISM: individual objects: NGC 1333 IRAS 4A
Record Number:CaltechAUTHORS:20140108-133159430
Persistent URL:http://resolver.caltech.edu/CaltechAUTHORS:20140108-133159430
Official Citation:Deep observations of O2 toward a low-mass protostar with Herschel-HIFI Umut A. Yıldız, Kinsuk Acharyya, Paul F. Goldsmith, Ewine F. van Dishoeck, Gary Melnick, Ronald Snell, René Liseau, Jo-Hsin Chen, Laurent Pagani, Edwin Bergin, Paola Caselli, Eric Herbst, Lars E. Kristensen, Ruud Visser, Dariusz C. Lis and Maryvonne Gerin A&A 558 A58 (2013) DOI: http://dx.doi.org/10.1051/0004-6361/201321944
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:43271
Collection:CaltechAUTHORS
Deposited By: Ruth Sustaita
Deposited On:08 Jan 2014 22:16
Last Modified:30 Aug 2017 21:44

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