Derivation of a large isotropic diffuse sky emission component at 1.25 and 2.2um from the COBE/DIRBE data

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Using all-sky maps obtained with COBE/DIRBE, we reanalyzed the diffuse sky brightness at 1.25 and 2.2 um, which consists of zodiacal light, diffuse Galactic light (DGL), integrated starlight (ISL), and isotropic emission including the extragalactic background light.

• Our new analysis including an improved estimate of the DGL and the ISL with the 2MASS data showed that deviations of the isotropic emission from isotropy were less than 10% in the entire sky at high Galactic latitude (|b|>35).
• The result of our analysis revealed a significantly large isotropic component at 1.25 and 2.2 um with intensities of 60.15 +/- 16.14 and 27.68 +/- 6.21 nWm-2sr-1, respectively.
• This intensity is larger than the integrated galaxy light, upper limits from gamma-ray observation, and potential contribution from exotic sources (i.e., Population III stars, intrahalo light, direct collapse black holes, and dark stars).