Herschel observations of extraordinary sources: Analysis of the HIFI 1.2 THz wide spectral survey toward orion KL. I. method
- Department of Astronomy, University of Michigan, 500 Church Street, Ann Arbor, MI 48109 (United States)
- Physikalisches Institut, Universität zu Köln, Zülpicher Str. 77, D-50937 Köln (Germany)
- Cahill Center for Astronomy and Astrophysics 301-17, California Institute of Technology, Pasadena, CA 91125 (United States)
- Centro de Astrobiología (CSIC/INTA), Laboratiorio de Astrofísica Molecular, Ctra. de Torrejón a Ajalvir, km 4, E-28850 Torrejón de Ardoz, Madrid (Spain)
- Division of Geological and Planetary Sciences, California Institute of Technology, MS 150-21, Pasadena, CA 91125 (United States)
- Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, CA 91109 (United States)
- Infrared Processing and Analysis Center, California Institute of Technology, MS 100-22, Pasadena, CA 91125 (United States)
- National Radio Astronomy Observatory, 520 Edgemont Road, Charlottesville, VA 22903 (United States)
- Division of Chemistry and Chemical Engineering, California Institute of Technology Pasadena, CA 91125 (United States)
- Department of Physics and Astronomy, University of Calgary, 2500 University Drive NW, Calgary, AB T2N 1N4 (Canada)
- SRON Netherlands Institute for Space Research, P.O. Box 800, 9700 AV Groningen (Netherlands)
We present a comprehensive analysis of a broadband spectral line survey of the Orion Kleinmann-Low nebula (Orion KL), one of the most chemically rich regions in the Galaxy, using the HIFI instrument on board the Herschel Space Observatory. This survey spans a frequency range from 480 to 1907 GHz at a resolution of 1.1 MHz. These observations thus encompass the largest spectral coverage ever obtained toward this high-mass star-forming region in the submillimeter with high spectral resolution and include frequencies >1 THz, where the Earth's atmosphere prevents observations from the ground. In all, we detect emission from 39 molecules (79 isotopologues). Combining this data set with ground-based millimeter spectroscopy obtained with the IRAM 30 m telescope, we model the molecular emission from the millimeter to the far-IR using the XCLASS program, which assumes local thermodynamic equilibrium (LTE). Several molecules are also modeled with the MADEX non-LTE code. Because of the wide frequency coverage, our models are constrained by transitions over an unprecedented range in excitation energy. A reduced χ{sup 2} analysis indicates that models for most species reproduce the observed emission well. In particular, most complex organics are well fit by LTE implying gas densities are high (>10{sup 6} cm{sup –3}) and excitation temperatures and column densities are well constrained. Molecular abundances are computed using H{sub 2} column densities also derived from the HIFI survey. The distribution of rotation temperatures, T {sub rot}, for molecules detected toward the hot core is significantly wider than the compact ridge, plateau, and extended ridge T {sub rot} distributions, indicating the hot core has the most complex thermal structure.
- OSTI ID:
- 22356785
- Journal Information:
- Astrophysical Journal, Vol. 787, Issue 2; Other Information: Country of input: International Atomic Energy Agency (IAEA); ISSN 0004-637X
- Country of Publication:
- United States
- Language:
- English
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