Spatial variations of the 3 micron emission features within UV-excited nebulae - Photochemical evolution of interstellar polycyclic aromatic hydrocarbons

Journal Article · Thu Jun 01 04:00:00 EDT 1989 · Astrophysical Journal; (USA)

DOI:https://doi.org/10.1086/167491· OSTI ID:5508752

Geballe, T R; Tielens, A G.G.M.; Allamandola, L J; Moorhouse, A; Brand, P W.J.L. ^[1]

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1. Joint Astronomy Center, Hilo, HI (USA)

Spectra at 3 microns have been obtained at several positions in the Orion Bar region and in the nebula surrounding HD 44179. Weak emission features at 3.40, 3.46, 3.51, and 3.57 microns are prominent in the Orion Bar region. The 3.40- and 3.51-micron features increase in intensity relative to the dominant 3.29-micron feature. The spectrum obtained in the Red Rectangle region 5 arcsecs north of HD 44179 are similar to those in the Orion Bar, with a weak, broad 3.40-micron feature at the position of HD 44179. The spatial behavior of the weak emission features is explained in terms of hot bands of the CH stretch and overtones, and combination bands of other fundamental vibrations in simple PAHs. Based on the susceptibility of PAHs to destruction by the far UV fields in both regions, PAH sizes are estimated at 20-50 carbon atoms. 38 refs.

• OSTI ID: 5508752
• Journal Information: Astrophysical Journal; (USA), Journal Name: Astrophysical Journal; (USA) Vol. 341; ISSN ASJOA; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

640105* -- Astrophysics & Cosmology-- Galaxies
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
AROMATICS
CHEMICAL COMPOSITION
CHEMICAL REACTIONS
CHEMISTRY
COSMOCHEMISTRY
ENERGY TRANSFER
HYDROCARBONS
INFRARED SPECTRA
INTERSTELLAR SPACE
LINE WIDTHS
MOLECULES
NEBULAE
ORGANIC COMPOUNDS
PHOTOCHEMICAL REACTIONS
SPACE
SPECTRA