Low-Resolution Spectrum of the Extragalactic Background Light with AKARI InfraRed Camera

TL;DR

This study presents a new measurement of the extragalactic background light in the 1.8-5.3 um range using AKARI, revealing excess emission over galaxy counts and providing independent validation of previous results.

Contribution

It offers the first independent EBL measurement in this wavelength range with AKARI, reducing Galactic star contamination and confirming previous findings.

Findings

Detected significant excess EBL over galaxy counts below 4 um.

Provided a new independent EBL measurement with AKARI's high sensitivity.

Confirmed consistency with previous IRTS and DIRBE measurements.

Abstract

The Extragalactic Background Light (EBL) as an integrated light from outside of our Galaxy includes information of the early universe and the Dark Ages. We analyzed the spectral data of the astrophysical diffuse emission obtained with the low-resolution spectroscopy mode on the AKARI Infra-Red Camera (IRC) in 1.8-5.3 um wavelength region. Although the previous EBL observation in this wavelength region is restricted to the observations by DIRBE and IRTS, this study adds a new independent result with negligible contamination of Galactic stars owing to higher sensitivity for point sources. Other two major foreground components, the zodiacal light (ZL) and the diffuse Galactic light (DGL), were subtracted by taking correlations with ZL brightness estimated by the DIRBE ZL model and with the 100 um dust thermal emission, respectively. The isotropic emission was obtained as EBL, which shows significant excess over integrated light of galaxies at <4 um. The obtained EBL is consistent with the previous measurements by IRTS and DIRBE.