Variations in the 3.3 µm feature and carbonaceous dust in AKARI data

Abstract

A wealth of near infrared spectroscopic data for a large number of galactic objects was recorded with AKARI during its active lifetime. The hydrocarbon emission features around 3.3 - 3.5 m are modelled here as a series of 6 Voigt profiles arising due to hydrogen atoms found in different molecular structures within the emitting spectroscopic carriers. This model is compared and contrasted with a model consisting of 3 Gaussian profiles and found to produce a superior fit to AKARI data. Analysis of the 6 Voigt model shows that the 3.3 m aromatic hydrocarbon band is well described by two components at 3.28 m and 3.30 m. We confirm that the 3.28 μm band is due to emission from aromatic molecules, and find a good correlation between the 3.28 μm and 3.41 m bands, assigned to bay-hydrogen sites and linking methylene groups respectively. Results are discussed in terms of molecular processing and dust formation.