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

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 3.3–3.5m 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 3.3m aromatic hydrocarbon band is well described by two components at 3.28m and 3.30m. We confirm that the 3.28μm band is due to emission from aromatic molecules, and find a good correlation between the 3.28μm and 3.41m bands, assigned to bay-hydrogen sites and linking methylene groups respectively. Results are discussed in terms of molecular processing and dust formation. •PAH emission at 3.3 μm is well modelled by two sub-features at 3.28 and 3.30 μm.•6 Voigt functions provide a better fit to the data than 3 Gaussian functions.•The 6 bands are assigned with help from literature values.•3.28 and 3.30µm features are very likely both due to aromatic hydrocarbon material.•3.28 and 3.41µm intensities are well correlated, suggesting a link.