Journal article
The Orion Fingers: H-2 Temperatures and Excitation in an Explosive Outflow
The Astrophysical journal, Vol.857(1), p.7
04/10/2018
DOI: 10.3847/1538-4357/aab4f4
Abstract
We measure H-2 temperatures and column densities across the Orion Becklin-Neugebauer/Kleinmann-Low (BN/KL) explosive outflow from a set of 13 near-infrared (IR) H-2 rovibrational emission lines observed with the TripleSpec spectrograph on Apache Point Observatory's 3.5 m telescope. We find that most of the region is well characterized by a single temperature (similar to 2000-2500 K), which may be influenced by the limited range of upper energy levels (6000-20,000 K) probed by our data set. The H-2 column density maps indicate that warm H-2 comprises 10(-5)-10(-3) of the total H-2 column density near the center of the outflow. Combining column density measurements for co-spatial H-2 and CO at T = 2500 K, we measure a CO/H-2 fractional abundance of 2 x 10(-3) and discuss possible reasons why this value is in excess of the canonical 10 (-4) value, including dust attenuation, incorrect assumptions on co-spatiality of the H-2 and CO emission, and chemical processing in an extreme environment. We model the radiative transfer of H-2 in this region with ultraviolet (UV) pumping models to look for signatures of H-2 fluorescence from H I Ly alpha pumping. Dissociative (J-type) shocks and nebular emission from the foreground Orion H II region are considered as possible Ly alpha sources. From our radiative transfer models, we predict that signatures of Ly alpha pumping should be detectable in near-IR line ratios given a sufficiently strong source, but such a source is not present in the BN/KL outflow. The data are consistent with shocks as the H-2 heating source.
Details
- Title: Subtitle
- The Orion Fingers: H-2 Temperatures and Excitation in an Explosive Outflow
- Creators
- Allison Youngblood - Laboratory for Atmospheric and Space PhysicsKevin France - Laboratory for Atmospheric and Space PhysicsAdam Ginsburg - National Radio Astronomy ObservatoryKeri Hoadley - California Institute of TechnologyJohn Bally - Laboratory for Atmospheric and Space Physics
- Resource Type
- Journal article
- Publication Details
- The Astrophysical journal, Vol.857(1), p.7
- Publisher
- Iop Publishing Ltd
- DOI
- 10.3847/1538-4357/aab4f4
- ISSN
- 0004-637X
- eISSN
- 1538-4357
- Number of pages
- 15
- Language
- English
- Date published
- 04/10/2018
- Academic Unit
- Physics and Astronomy
- Record Identifier
- 9984428794902771
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