Irts Observations of the Near-infrared Extragalactic Background Light

Abstract

We have searched for near-infrared extragalactic background light (EBL) in the data from the Near-InfraRed Spectrometer (NIRS) on the Infrared Telescope in Space (IRTS). After subtracting the contribution of faint stars and the zodiacal component based on modeling, a significant isotropic emission is obtained in the wavelength bands from 1.4 μm to 4.0 μm. The spectrum is stellar-like, but shows a spectral jump from the optical EBL. The emission obtained is isotropic over the observed sky, and the in-band flux amounts to ∼ 35 nWmsr which is too bright to be explained by the integrated light from faint galaxies. Analyses of COBE/DIRBE data, after removal of starlight, show essentially the same result within the uncertainty in the zodiacal light model, which implies that the isotropic emission observed by IRTS/NIRS is of extragalactic origin. Significant fluctuations in sky brightness were also detected which cannot be explained by fluctuations due to faint stars, zodiacal components and normal galaxies. The excess fluctuation amounts to ∼ 1/4 of the excess emission over the integrated light of galaxies and is consistent with fluctuations observed by COBE/DIRBE. A two-point Present address is National Astronomical Observatory of Japan, Mitaka 181-8588, Japan Now out of ISAS/JAXA

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Cite this paper

@inproceedings{Matsumoto2005IrtsOO, title={Irts Observations of the Near-infrared Extragalactic Background Light}, author={Takuma Matsumoto and Saki Matsuura and Hirokatsu Murakami and Motonobu Tanaka and Michael Freund and Mikyung Lim and Mitsunobu Kawada and Masashi Noda}, year={2005} }