Updated analysis of near-infrared background fluctuations

Abstract

The power spectrum of Near InfraRed Background (NIRB) fluctuations measured at 3.6 $\mu$m by {\tt Spitzer} shows a clustering excess over the known galaxies signal that has been interpreted in terms of early ($z\simgt 13$), accreting (direct collapse) black holes (DCBH) or low-$z$ intrahalo light (IHL). In addition, these fluctuations correlate with the cosmic X-ray background (CXB) measured at (0.5-2) keV, supporting the black hole explanation. This scenario has been questioned by the recent detection of a correlation between the two {\tt CIBER} 1.1/1.6 $\mu$m bands with the 3.6 $\mu$m {\tt Spitzer} one. This correlation is hardly explained by early DCBHs that, due to intergalactic absorption, cannot contribute to the shortest wavelength bands. Here we show that the new correlation is caused instead by a Diffuse Galactic Light (DGL) component arising from Galactic stellar light scattered by dust. The black hole interpretation of the excess remains perfectly valid and, actually, the inclusion of DGL allows less demanding (by up to about 30\%) requirements on the DCBH abundance/mass.