EAS Publications Series
Volume 46, 2011PAHs and the Universe: A Symposium to Celebrate the 25th Anniversary of the PAH Hypothesis
|Page(s)||117 - 122|
|Published online||30 March 2011|
C. Joblin and A.G.G.M. Tielens (eds)
EAS Publications Series, 46 (2011) 117-122
Analyzing astronomical observations with the NASA Ames PAH database
Department of Physics and Astronomy, University of Western
2 SETI Institute - 189 Bernardo Ave., Suite 100 - Mountain View, CA 94043, USA
We use the NASA Ames Polycyclic Aromatic Hydrocarbon (PAH) infrared spectroscopic database to model infared emission of PAHs following absorption of a UV photon. We calculate emission spectra resulting from the full cooling cascade for each species in the database. Using a least squares approach, we can find out what PAH mixtures best reproduce a few typical astronomical observations representing the different classes of UIR spectra. We find that we can reproduce the observed UIR spectra in the wavelength range 6–14 μm, offering support for the hypothesis that the UIR bands are indeed due to vibrational modes of PAHs and related molecular species. Spectral decompositions of our best fit models confirm and reinforce several earlier results: (i) the 6.2 μm band requires a significant contribution of nitrogen-substituted PAHs (PANHs); (ii) the reported components and their variations in the 7.7 μm band are indicative of changes in the size distribution of the contributing molecules; (iii) there is a significant contribution of anions to the 7.7 μm band; (iv) the 11.2 μm band is due to large, neutral and pure PAHs; (v) the 11.0 μm band is due to large PAH cations.
© EAS, EDP Sciences 2011
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