Polycyclic Aromatic Hydrocarbons in space

Els Peeters, Associate Professor, Physics & Astronomy

The infrared spectra of most galactic and extragalactic sources are dominated by infrared emission features at 3.3, 6.2, 7.7, 8.6 and 11.2 micron, the so-called unidentified infrared (UIR) bands. These emission features are generally attributed to Polycyclic Aromatic Hydrocarbon molecules (PAHs) and closely related species. These PAH bands have been found in a wide variety of environments throughout the Universe and contain up to 10% of the total power output of star-forming galaxies. 

Space-based telescopes such as the Infrared Space Observatory (ISO) and the Spitzer Space Telescope revealed the richness of the PAH spectrum and provided extensive evidence for significant variability in the PAH spectrum from source to source and spatially within sources. In this talk, I will discuss the spectral characteristics of astronomical PAHs, their dependence on the local environments and the implications for the characteristics of the carriers.