AKARI observation of the fluctuation of the near-infrared background
  We report a search for fluctuations of the sky brightness toward the north
ecliptic pole (NEP) with the Japanese infrared astronomical satellite AKARI,at
2.4, 3.2, and 4.1 \mum. We obtained circular maps with 100 diameter field of
view which clearly show a spatial structure on scale of a few hundred arcsec. A
power spectrum analysis shows that there is a significant excess fluctuation at
angular scales larger than 10000 that can't be explained by zodiacal light,
diffuse Galactic light, shot noise of faint galaxies or clustering of low
redshift galaxies. These results are consistent with observations at 3.6 and
4.5 \mum by NASA's Spitzer Space Telescope. The fluctuating component observed
at large angular scales has a blue stellar spectrum which is similar to that of
the spectrum of the excess isotropic emission observed with IRTS. A significant
spatial correlation between wavelength bands was found, and the slopes of the
linear correlations is consistent with the spectrum of the excess fluctuation.
These findings indicate that the detected fluctuation could be attributed to
the first stars of the universe, i.e. pop. III stars. The observed fluctuation
provides an important constraints on the era of the first stars.
