Interpreting the subtle spectral variations of the 11.2 and 12.7 μm polycyclic aromatic hydrocarbon bands

Abstract

We report new properties of the 11 and 12.7 μm emission complexes of polycyclic aromatic hydrocarbons (PAHs) by applying a Gaussian-based decomposition technique. Using high-resolution \textit{Spitzer} Space Telescope data, we study in detail the spectral and spatial characteristics of the 11 and 12.7 μm emission bands in maps of reflection nebulae NGC 7023 and NGC 2023 (North and South) and the star-forming region M17. Profile variations are observed in both the 11 and 12.7 μm emission bands. We identify a neutral contribution to the traditional 11.0 μm PAH band and a cationic contribution to the traditional 11.2 μm band, the latter of which affects the PAH class of the 11.2 μm emission in our sample. The peak variations of the 12.7 μm complex are explained by the competition between two underlying blended components. The spatial distributions of these components link them to cations and neutrals. We conclude that the 12.7 μm emission originates in both neutral and cationic PAHs, lending support to the use of the 12.7/11.2 intensity ratio as a charge proxy.

20 pages, 14 figures, Accepted for publication in ApJ

References in corpus (32)

• scikit-image: Image processing in Python
• The Spitzer Space Telescope Mission
• The Infrared Spectrograph on the Spitzer Space Telescope
• The Mid-Infrared Spectrum of Star-Forming Galaxies: Global Properties of PAH Emission
• The rich 6 to 9 um spectrum of interstellar PAHs
• Mid-IR Galaxy Classification Based on Silicate Obscuration and PAH Equivalent Width
• The CH out-of-plane bending modes of PAH molecules in astrophysical environments
• Formation of buckminsterfullerene (C60) in interstellar space
• Variations of the Mid-IR Aromatic Features Inside and Among Galaxies
• The profiles of the 3 to 12 $\mu$m PAH features
• Pixie Dust: The Silicate Features in the Diffuse Interstellar Medium
• Spectral Mapping Reconstruction of Extended Sources
• Analysis of the emission of very small dust particles from Spitzer spectro-imagery data using blind signal separation methods
• The infrared spectra of very large, compact, highly symmetric, polycyclic aromatic hydrocarbons (PAHs)
• The Infrared Spectra of Very Large Irregular Polycyclic Aromatic Hydrocarbons (PAHs): Observational Probes of Astronomical PAH Geometry, Size and Charge
• The unusual hydrocarbon emission from the early carbon star HD 100764: The connection between aromatics and aliphatics
• Formation and destruction of polycyclic aromatic hydrocarbon clusters in the interstellar medium
• Trigonometric Parallaxes of Massive Star Forming Regions: VIII. G12.89+0.49, G15.03-0.68 (M17) and G27.36-0.16
• ISO spectroscopy of compact HII regions in the Galaxy. II Ionization and elemental abundances
• Carbon-rich dust past the asymptotic giant branch: aliphatics, aromatics, and fullerenes in the Magellanic Clouds
• The 15 - 20 Micron Spitzer Spectra of Interstellar Emission Features in NGC 7023
• Direct spectroscopic evidence for ionized PAHs in the interstellar medium
• The 15-20 um emission in the reflection nebula NGC2023
• Coupled Blind Signal Separation and Spectroscopic Database Fitting of the Mid Infrared PAH Features
• Spatial distribution and interpretation of the 3.3 \mum PAH emission band of the Red Rectangle
• The 11.2 $\mu$m emission of PAHs in astrophysical objects
• [SiPAH]+ pi-Complexes in the Interstellar Medium
• Polycyclic Aromatic Hydrocarbon emission in Spitzer/IRS maps I: Catalog and simple diagnostics
• Probing the Ionization States of Polycyclic Aromatic Hydrocarbons via the 15-20 μm Emission Bands
• The mid-infrared appearance of the Galactic Mini-Starburst W49A
• PDR Model Mapping of Obscured H2 Emission and the Line-of-Sight Structure of M17-SW
• Extinction and PAH intensity variations across the HII region IRAS 12063-6259

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• IRMPD spectroscopy of a PAH cation using FELICE: The infrared spectrum and photodissociation of dibenzo[a,l]pyrene
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• JWST observations of photodissociation regions. IV. Carbonaceous emission band sub-components in NGC 7023 have distinct spatial distributions
• Characterizing the PAH Emission in the Orion Bar
• PDRs4All XIX. The 6 to 9 $\mu$m region as a probe of PAH charge and size in the Orion Bar