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Session 16 - Interstellar Grains, PAH's and the Interstellar Bands.
Display session, Monday, January 13
Polycyclic aromatic hydrocarbons (PAHs) have been generally accepted as the most likely explanation for the unidentified infrared (UIR) bands. These emission features are observed in IRAS sources such as asymptotic giant branch (AGB) circumstellar shells, and planetary nebulae (PNe). IR absorption bands observed in the diffuse interstellar medium (DIM) can be reproduced by some forms of hydrogenated amorphous carbon (HAC). Our laboratory experiments have shown that PAH absorption features emerge in the IR spectrum of thermally annealed HAC prior to decomposition. These features have now been observed in emission and are compared to various UIR spectra. Observations have shown that PAH emission features are enhanced in ionization and shock fronts, providing evidence for a connection between HAC and PAH in these objects.
This research was supported by grants from the NSERCC
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