Low-Resolution Spectrum of the Diffuse Galactic Light and 3.3µm PAH Emission with the AKARI InfraRed Camera

Abstract

We first obtained the spectrum of the diffuse Galactic light (DGL) at general interstellar space in the $1.8-5.3 \mu \textrm m $ wavelength region with the low-resolution prism spectroscopy mode of the AKARI Infra-Red Camera (IRC) NIR channel. The $3.3 \mu \textrm m $ PAH band is detected in the DGL spectrum at Galactic latitude $\mid b \mid \lt 15^{\circ}$, and its correlations with the Galactic dust and gas are confirmed. The correlation between the $3.3 \mu \textrm m $ PAH band and the thermal emission from the Galactic dust is expressed not by a simple linear correlation, but by a relation with extinction. Using this correlation, the spectral shape of DGL at an optically thin region ($5^{\circ} \lt \mid b \mid \lt 15^{\circ}$) was derived as a template spectrum. Assuming that the spectral shape of this template spectrum is uniform at any position, the DGL spectrum can be estimated by scaling this template spectrum using the correlation between the $3.3 \mu \textrm m $ PAH band and the thermal emission from the Galactic dust.