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Revisiting Polycyclic Aromatic Hydrocarbon Emission In Photodissociation Regions, Ameek K. Sidhu
Revisiting Polycyclic Aromatic Hydrocarbon Emission In Photodissociation Regions, Ameek K. Sidhu
Electronic Thesis and Dissertation Repository
The mid-infrared (IR) spectrum of almost all objects in the Universe is dominated by a set of strong emission features characteristic of a class of large organic molecules made of carbon and hydrogen known as polycyclic aromatic hydrocarbons (PAHs). These molecules account for ~15% of the cosmic carbon and ~20% of the total IR power of the Milky Way and star-forming galaxies. They are strong absorbers of ultraviolet (UV) photons and release the absorbed energy through vibrational transitions that result in strong IR emission features. PAHs play a critical role in the evolution of the interstellar medium (ISM) as they …
Mid-Infrared Studies Of Galactic Sources: Probing The Relationship Between Polycyclic Aromatic Hydrocarbons And Their Physical Environment, Collin Matthew Knight
Mid-Infrared Studies Of Galactic Sources: Probing The Relationship Between Polycyclic Aromatic Hydrocarbons And Their Physical Environment, Collin Matthew Knight
Electronic Thesis and Dissertation Repository
Over the past 50 years, prominent mid-infrared (MIR) emission features from 3--20 $\mu$m have been observed ubiquitously in the interstellar medium (ISM) of Galactic and extragalactic sources. These emission features arise from the vibrational relaxation of polycyclic aromatic hydrocarbons (PAHs) after the absorption of a far-ultraviolet (FUV) photon. PAHs are astronomically significant in that they contain up to 15\% of the cosmic carbon inventory and play an important role in the physical and chemical processes of the ISM such as, for example, the gas heating and the ionization balance. Variations in the relative strengths of the major PAH bands can …