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

TL;DR

This study presents the first low-resolution spectrum of diffuse Galactic light in the 1.8-5.3 um range, detecting the 3.3 um PAH emission and establishing its correlation with Galactic dust and gas, providing a spectral template for DGL.

Contribution

It introduces the first spectrum of DGL in this wavelength range and models its relation with dust and gas, enabling estimation of DGL spectra across different regions.

Findings

Detection of 3.3 um PAH emission in DGL spectrum.

Correlation between PAH emission and Galactic dust with extinction dependence.

Derived a spectral template for DGL in optically thin regions.

Abstract

We first obtained the spectrum of the diffuse Galactic light (DGL) at general interstellar space in 1.8-5.3 um wavelength region with the low-resolution prism spectroscopy mode of the AKARI Infra-Red Camera (IRC) NIR channel. The 3.3 um PAH band is detected in the DGL spectrum at Galactic latitude |b| < 15 deg, and its correlations with the Galactic dust and gas are confirmed. The correlation between the 3.3 um 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 optically thin region (5 deg < |b| < 15 deg) was derived as a template spectrum. Assuming that the spectral shape of this template spectrum is uniform at any position, DGL spectrum can be estimated by scaling this template spectrum using the correlation between the 3.3 um PAH band and the thermal emission from the Galactic dust.