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The Photochemical Evolution of the PAH Family in Photo-Dissociation Regions.
Wednesday, November 06, 2019 - 3:30pm PST
University of Western Ontario
The mid-IR spectra of photodissociation regions (PDRs) are dominated by the well-known emission features at 3.3, 6.2, 7.7, 11.3, and 12.7 micron, generally attributed to polycyclic aromatic hydrocarbon molecules (PAHs). PAHs drive much of the physics and the chemistry in these PDRs, e.g. by heating the gas and as a catalyst in the formation of molecular hydrogen on their surfaces. Thus, PAHs and PDRs are intimately connected, and a complete knowledge of PDRs requires a good understanding of the properties of the PAH population.
In this talk, I will review the rich complexity and variability of the astronomical PAH emission and their dependence on key physical parameters, including theoretical and experimental studies of PAHs that guide the interpretation of their observational behaviour. I will highlight how these studies provide a unique view of the photochemical evolution of large carbonaceous materials in space. Finally, I will present an Early Release Science program with the James Webb Space Telescope (JWST) that is geared toward spatially resolving the infrared emission from the star-forming region the Orion Bar in order to characterize simultaneously the physical conditions, the PAH characteristics, and the chemical processes at play.