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Analysis of the Herschel/HEXOS Spectral Survey Towards Orion South: A massive protostellar envelope with strong external irradiation

Tahani, K. and Plume, R. and Bergin, E. A. and Tolls, V. and Phillips, T. G. and Caux, E. and Cabrit, S. and Goicoechea, J. R. and Goldsmith, P. F. and Johnstone, D. and Lis, D. C. and Pagani, L. and Menten, K. M. and Müller, H. S. P. and Ossenkopf-Okada, V. and Pearson, J. C. and van der Tak, F. F. S. (2016) Analysis of the Herschel/HEXOS Spectral Survey Towards Orion South: A massive protostellar envelope with strong external irradiation. Astrophysical Journal, 832 (1). Art. No. 12. ISSN 0004-637X.

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We present results from a comprehensive submillimeter spectral survey toward the source Orion South, based on data obtained with the Heterodyne Instrument for the Far-Infrared instrument on board the Herschel Space Observatory, covering the frequency range of 480 to 1900 GHz. We detect 685 spectral lines with signal-to-noise ratios (S/Ns) > 3σ, originating from 52 different molecular and atomic species. We model each of the detected species assuming conditions of Local Thermodynamic Equilibrium. This analysis provides an estimate of the physical conditions of Orion South (column density, temperature, source size, and V_(LSR)). We find evidence for three different cloud components: a cool (T_(ex) ~ 20–40 K), spatially extended (>60"), and quiescent (ΔV_(FWHM) ~ 4 km s^(−1)) component; a warmer (T_(ex) ~ 80–100 K), less spatially extended (~30"), and dynamic (ΔV_(FWHM) ~ 8 km s^(−1)) component, which is likely affected by embedded outflows; and a kinematically distinct region (T_(ex) > 100 K; V_(LSR) ~ 8 km s^(−1)), dominated by emission from species that trace ultraviolet irradiation, likely at the surface of the cloud. We find little evidence for the existence of a chemically distinct "hot-core" component, likely due to the small filling factor of the hot core or hot cores within the Herschel beam. We find that the chemical composition of the gas in the cooler, quiescent component of Orion South more closely resembles that of the quiescent ridge in Orion-KL. The gas in the warmer, dynamic component, however, more closely resembles that of the Compact Ridge and Plateau regions of Orion-KL, suggesting that higher temperatures and shocks also have an influence on the overall chemistry of Orion South.

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Lis, D. C.0000-0002-0500-4700
Additional Information:© 2016 American Astronomical Society. Received 2016 May 30. Accepted 2016 August 16. Published 2016 November 11. HIFI was designed and built by a consortium of institutes and university departments from across Europe, Canada, and the United States under the leadership of the 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. We also need to acknowledge the support by the Deutsche Forschungsgemeinschaft (DFG) via the collaborative research grant SFB 956, project C1 & C3, as well as the ERC and the Spanish MINECO for funding support under grants ERC-2013-Syg-610256 and AYA2012-32032. Support for this work was provided, in part, by a National Sciences and Engineering Research Council of Canada (NSERC) grant to R. Plume and K. Tahani and by NASA through an award issued by JPL/Caltech. This work was carried out in part at the Jet Propulsion Laboratory, which is operated for NASA by the California Institute of Technology. Facility: Herschel - European Space Agency's Herschel space observatory.
Funding AgencyGrant Number
Deutsche Forschungsgemeinschaft (DFG)SFB 956 project (C1 & C3)
European Research Council (ERC)ERC-2013-Syg-610256
Ministerio de Economía, Industria y Competitividad (MINECO)AYA2012-32032
National Sciences and Engineering Research Council of Canada (NSERC)UNSPECIFIED
Subject Keywords:ISM: abundances; ISM: individual objects (Orion South) ; ISM: kinematics and dynamics; ISM: lines and bands; ISM: molecules
Record Number:CaltechAUTHORS:20161117-070502665
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Official Citation:K. Tahani et al 2016 ApJ 832 12
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:72084
Deposited By: Ruth Sustaita
Deposited On:17 Nov 2016 17:18
Last Modified:30 Aug 2017 20:56

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