Infrared Extragalactic Background Light

Abstract

Infrared extragalactic background light plays an important role in the study of the early history of the universe, especially as a probe to search for the primeval galaxies. In the near-infrared region, UV and visible light emitted from high redshift galaxies could be observable. Measurement of the sky fluctuation at 2.2 μm gives a very low upper limit. The rocket observation of the near-infrared diffuse emission reveals isotropic emission which is possibly ascribed to an extragalactic origin. The observed brightness and fluctuation are not consistent with the standard scenario of the primeval galaxies. In the far-infrared region, integrated light of dust emission of the distant galaxies forms another cosmic background radiation. IRAS and the Nagoya-Berkeley rocket experiment found a clear correlation between HI column density and far-infrared sky brightness; however, there remains an uncorrelated isotropic emission component. If we ascribe this emission to extragalactic origin, a fairly big evolution effect is required. In the submillimeter region, excess emission over the 2.74K blackbody spectrum was found, which requires the vast energy generation in the early universe.