The 3.3 $\mu$m PAH emission band of the Red Rectangle

TL;DR

This study analyzes the 3.3 μm PAH emission in the Red Rectangle nebula, revealing a two-component structure with temperature-dependent wavelength shifts, supported by observational data and laboratory comparisons.

Contribution

It introduces a two-component interpretation for the 3.3 μm PAH feature and demonstrates its applicability across different nebulae using spectral data.

Findings

Two distinct emission components near 3.28 μm and 3.30 μm.

Wavelength shifts indicating decreasing carrier temperature with distance.

Consistent results across multiple nebulae and laboratory data.

Abstract

A new analysis of long-slit CGS4 (UKIRT) spectra of the 3.3 $\mu$m feature of the Red Rectangle and its evolution with offset along the NW whisker of the nebula is presented. The results support a proposed two-component interpretation for the 3.3 $\mu$m feature with peak wavelengths near 3.28 $\mu$m and 3.30 $\mu$m. Both components exhibit a small shift to shorter wavelength with increasing offset from the central star which, by comparison with laboratory studies, is consistent with a decrease in temperature of the carriers with distance from HD 44179. The two-component approach is also applied to 3.3 $\mu$m data for the Red Rectangle, Orion Bar D2 and Orion Bar H2S1 from ISO SWS studies.