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Herschel Measurements of Molecular Oxygen in Orion
- Source :
- Astrophysical Journal, 737(2):96. IOP PUBLISHING LTD, The Astrophysical Journal, The Astrophysical Journal, American Astronomical Society, 2011, 737, pp.96. ⟨10.1088/0004-637X/737/2/96⟩, The Astrophysical Journal, 2011, 737, pp.96. ⟨10.1088/0004-637X/737/2/96⟩
- Publication Year :
- 2011
-
Abstract
- International audience; We report observations of three rotational transitions of molecular oxygen (O2) in emission from the H2 Peak 1 position of vibrationally excited molecular hydrogen in Orion. We observed the 487 GHz, 774 GHz, and 1121 GHz lines using the Heterodyne Instrument for the Far Infrared on the Herschel Space Observatory, having velocities of 11 km s-1 to 12 km s-1 and widths of 3 km s-1. The beam-averaged column density is N(O2) = 6.5 × 1016 cm-2, and assuming that the source has an equal beam-filling factor for all transitions (beam widths 44, 28, and 19''), the relative line intensities imply a kinetic temperature between 65 K and 120 K. The fractional abundance of O2 relative to H2 is (0.3-7.3) × 10-6. The unusual velocity suggests an association with a ~5'' diameter source, denoted Peak A, the Western Clump, or MF4. The mass of this source is ~10 M sun and the dust temperature is >=150 K. Our preferred explanation of the enhanced O2 abundance is that dust grains in this region are sufficiently warm (T >= 100 K) to desorb water ice and thus keep a significant fraction of elemental oxygen in the gas phase, with a significant fraction as O2. For this small source, the line ratios require a temperature >=180 K. The inferred O2 column density sime5 × 1018 cm-2 can be produced in Peak A, having N(H2) ~= 4 × 1024 cm-2. An alternative mechanism is a low-velocity (10-15 km s-1) C-shock, which can produce N(O2) up to 1017 cm-2. Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA.
- Subjects :
- ROTATIONAL-EXCITATION
WAVE-ASTRONOMY-SATELLITE
DISSOCIATIVE RECOMBINATION
Mean kinetic temperature
Abundance (chemistry)
FOS: Physical sciences
Astrophysics
7. Clean energy
01 natural sciences
ISM: abundances
ISM: individual objects (Orion)
O-2 ABUNDANCE
UPPER LIMITS
0103 physical sciences
010303 astronomy & astrophysics
Line (formation)
ISM: individual objects: Orion
Physics
DENSE INTERSTELLAR CLOUDS
GAS-PHASE CHEMISTRY
010308 nuclear & particles physics
Filling factor
astrochemistry
Astronomy and Astrophysics
Elemental oxygen
INTER-STELLAR CLOUDS
APERTURE SYNTHESIS
Astrophysics - Astrophysics of Galaxies
ISM: molecules
[PHYS.ASTR.GA]Physics [physics]/Astrophysics [astro-ph]/Galactic Astrophysics [astro-ph.GA]
13. Climate action
Space and Planetary Science
Astrophysics of Galaxies (astro-ph.GA)
Excited state
submillimeter: ISM
[SDU.ASTR.GA]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Galactic Astrophysics [astro-ph.GA]
Molecular oxygen
INELASTIC-COLLISIONS
Beam (structure)
Subjects
Details
- Language :
- English
- ISSN :
- 0004637X and 15384357
- Volume :
- 737
- Issue :
- 2
- Database :
- OpenAIRE
- Journal :
- Astrophysical Journal
- Accession number :
- edsair.doi.dedup.....ee372949fcd1e495fae6345ff9c1d4d7