The 11.2 $\mu$m emission of PAHs in astrophysical objects

Abstract

The 11.2 $\mu$m emission band belongs to the family of the `Unidentified' Infrared (UIR) emission bands seen in many astronomical environments. In this work we present a theoretical interpretation of the band characteristics and profile variation for a number of astrophysical sources in which the carriers are subject to a range of physical conditions. The results of Density Functional Theory (DFT) calculations for the solo out-of-plane (OOP) vibrational bending modes of large polycyclic aromatic hydrocarbon (PAH) molecules are used as input for a detailed emission model which includes the temperature and mass dependence of PAH band wavelength, and a PAH mass distribution that varies with object. Comparison of the model with astronomical spectra indicates that the 11.2 $\mu$m band asymmetry and profile variation can be explained principally in terms of the mass distribution of neutral PAHs with a small contribution from anharmonic effects.

13 pages, 10 figures, 3 table. Accepted for publication in MNRAS

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• Theoretical study of infrared spectra of interstellar PAH molecules with N, NH & NH${}_2$ incorporation
• A Small Fullerene (C24) may be the Carrier of the 11.2 micron Unidentified Infrared Band
• Probing computational methodologies in predicting mid-infrared spectra for large polycyclic aromatic hydrocarbons
• Polycyclic Aromatic Hydrocarbon emission model in photodissociation regions I: Application to the 3.3, 6.2, and 11.2 $\mu$m bands
• Profile comparison of the 6-9 $\mu$m polycyclic aromatic hydrocarbon bands in starburst-dominated galaxies
• Investigating dusty Red Supergiant outflows in Westerlund 1 with 3D Hydrodynamic simulations
• IRMPD spectroscopy of a PAH cation using FELICE: The infrared spectrum and photodissociation of dibenzo[a,l]pyrene
• Searching for Corannulene with ALMA: Observations of the Red Rectangle Nebula
• Variations in the 6.2 $\mu$m polycyclic aromatic hydrocarbon band in Active Galactic Nuclei- and Starburst-dominated galaxies
• JWST observations of photodissociation regions. IV. Carbonaceous emission band sub-components in NGC 7023 have distinct spatial distributions