Infrared Telescope in Space Observations of the Near-Infrared Extragalactic Background Light

By T. Matsumoto, S. Matsuura, H. Murakami, Masahiro Tanaka, M. Freund, M. Lim, Marvin L. Cohen, M. Kawada, M. Noda. 2004

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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 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 nW m-2 sr-1, 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 that 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 correlation analysis shows that IRTS NIRS data have an angular scale of fluctuations of a few degrees. The spectrum and brightness of the observed excess EBL emission could be explained by the redshifted UV radiation from the first generation of massive stars (Population III stars), which caused the reionization of the universe. Recent Wilkinson Microwave Anisotropy Probe (WMAP) observations of the cosmic microwave background (CMB) polarization have indicated that reionization occurred at z ~ 17 or earlier, while the spectral jump around 1 μm in the observed excess EBL suggests that the Population III star formation terminated at z ~ 9. The observed fluctuations, however, are considerably larger than the theoretical predictions for the Population III stars.

Subfields: Astronomy and Astrophysics, Nuclear and High Energy Physics

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Citations in the corpus

New limits on the density of the extragalactic background light in the optical to the far-infrared from the spectra of all known TeV blazars (2007, background): “As stated for the individual spectrum the NIR excess claimed by Matsumoto et al. (2005) for wavelengths above 2µm is now compatible with the limit, but for shorter wavelengths it isstill clearly excluded.”
Semi-analytic modeling of the EBL and consequences for extragalactic gamma-ray spectra (2011, methodology): “The small cyan points are from direct photometry with the IRTS satellite (Matsumoto et al. 2005).”
The extragalactic background light and the gamma-ray opacity of the universe (2012, background): “Extreme EBL scenarios, with 70 nW m−2 sr−1at 1.5 µm, as suggested by Matsumoto et al. (2005) are clearly ruled out.”
Cosmological Magnetic Fields: Their Generation, Evolution and Observation (2013, background): “…tight lower bounds on the EBL density at different wavelengths were derived from the observations with telescopes in space and on the ground (Elbaz et al 2002; Matsumoto et al 2005; Frayer et al 2006; Dole et al 2006; Kashlinsky et al 2012; Berta et al 2010; Oliver et al 2010; Keenan et al 2010).”
Semi-analytic modelling of the extragalactic background light and consequences for extragalactic gamma-ray spectra: Modelling of the EBL and gamma-ray spectra (2012, methodology): “The small cyan points are from direct photometry with the IRTS satellite (Matsumoto et al. 2005).”
Extragalactic optical-infrared background radiation, its time evolution and the cosmic photon-photon opacity (2008, methodology): “1 indicated by the IRTS observations of Matsumoto et al. (2005) may be explained in principle by the conversion of a fraction f∗ of all baryons into very massive stars producing photons with an efficiencyǫ.”
Intergalactic Photon Spectra from the Far-IR to the UV Lyman Limit for 0 < z < 6 and the Optical Depth of the Universe to High-Energy Gamma Rays (2005, background): “A reported near-IR excess (Matsumoto et al. 2005) conflicts with upper limits from TeV blazar spectra (Schroedter 2005) and is also inconsistent with galaxy counts and theoretical models of early star formation.”