ANALYSIS OF THE HERSCHEL /HEXOS SPECTRAL SURVEY TOWARD ORION SOUTH: A MASSIVE PROTOSTELLAR ENVELOPE WITH STRONG EXTERNAL IRRADIATION

Journal Article · Sun Nov 20 04:00:00 EST 2016 · Astrophysical Journal

DOI:https://doi.org/10.3847/0004-637X/832/1/12· OSTI ID:22667198

Tahani, K.; Plume, R. ^[1]; Bergin, E. A. ^[2]; Tolls, V. ^[3]; Phillips, T. G.; Lis, D. C. ^[4]; Caux, E. ^[5]; Cabrit, S.; Pagani, L. ^[6]; Goicoechea, J. R. ^[7]; Goldsmith, P. F.; Pearson, J. C. ^[8]; Johnstone, D. ^[9]; Menten, K. M. ^[10]; Müller, H. S. P.; Ossenkopf-Okada, V. ^[11]

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1. Department of Physics and Astronomy, University of Calgary, Calgary, AB T2N 1N4 (Canada)
2. Department of Astronomy, University of Michigan, 500 Church Street, Ann Arbor, MI 48109 (United States)
3. Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States)
4. California Institute of Technology, Cahill Center for Astronomy and Astrophysics 301-17, Pasadena, CA 91125 (United States)
5. Université de Toulouse, UPS-OMP, IRAP, F-31028 Toulouse (France)
6. LERMA, Observatoire de Paris, PSL Research University, CNRS, Sorbonne Universités, UPMC Univ. Paris 06, F-75014, Paris (France)
7. Instituto de Ciencia de Materiales de Madrid (ICMM-CSIC). Sor Juana Ines de la Cruz 3, E-28049 Cantoblanco, Madrid (Spain)
8. Jet Propulsion Laboratory, Caltech, Pasadena, CA 91109 (United States)
9. National Research Council Canada, Herzberg Institute of Astrophysics, 5071 West Saanich Road, Victoria, BC V9E 2E7 (Canada)
10. Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, D-53121 Bonn (Germany)
11. I. Physikalisches Institut, Universität zu Köln, Zülpicher Strasse 77, D-50937 Köln (Germany)

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) > 3 σ , 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 {sub LSR}). We find evidence for three different cloud components: a cool ( T {sub ex} ∼ 20–40 K), spatially extended (>60″), and quiescent (Δ V {sub FWHM} ∼ 4 km s{sup -1}) component; a warmer ( T {sub ex} ∼ 80–100 K), less spatially extended (∼30″), and dynamic (Δ V {sub FWHM} ∼ 8 km s{sup -1}) component, which is likely affected by embedded outflows; and a kinematically distinct region ( T {sub ex} > 100 K; V {sub LSR} ∼ 8 km s{sup -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.

• OSTI ID: 22667198
• Journal Information: Astrophysical Journal, Journal Name: Astrophysical Journal Journal Issue: 1 Vol. 832; ISSN ASJOAB; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
ABUNDANCE
BEAMS
CLOUDS
DENSITY
EMISSION
EXTERNAL IRRADIATION
GHZ RANGE
HEAT EXCHANGERS
LTE
MOLECULES
NOISE
SIGNAL-TO-NOISE RATIO
SPACE
SURFACES
THERMODYNAMICS
ULTRAVIOLET RADIATION