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A New 3.25 Micron Absorption Feature toward Mon R2/IRS-3

K. Sellgren·T. Y. Brooke·R. G. Smith
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Abstract

A new 3.2--3.5~$μ$m spectrum of the protostar Mon~R2/IRS-3 confirms our previous tentative detection of a new absorption feature near 3.25 $μ$m. The feature in our new spectrum has a central wavelength of 3.256 $μ$m (3071 cm$^{-1}$) and has a full-width at half maximum of 0.079 $μ$m (75 cm$^{-1}$). We explore a possible identification with aromatic hydrocarbons at low temperatures, which absorb at a similar wavelength. If the feature is due to aromatics, the derived column density of C--H bonds is $\sim$1.8 $\times$ $10^{18}$ cm$^{-2}$. If the absorbing aromatic molecules are of roughly the same size as those responsible for aromatic emission features in the interstellar medium, then we estimate that $\sim$9\% of the cosmic abundance of carbon along this line of sight would be in aromatic hydrocarbons, in agreement with abundance estimates from emission features.

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K. Sellgren, T. Y. Brooke, R. G. Smith. 1995-08-11. A New 3.25 Micron Absorption Feature toward Mon R2/IRS-3. https://doi.org/10.1086/309627

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