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Angular fluctuations of the Near InfraRed Background (NIRB) intensity are observed up to scales 1^^{}. Their interpretation is challenging as even after removing the contribution from detected sources, the residual signal is >10 times higher than expected from distant galaxies below the detection limit and first stars. We propose here a novel interpretation in which early, intermediate mass, accreting direct collapse black holes (DCBH), which are too faint to be detected individually in current surveys, could explain the observed fluctuations. We find that a population of highly obscured (N ₇ 10^25 cm^-2) DCBHs formed in metal-free halos with virial temperature 10⁴ K at z 12, can explain the observed level 10^-3 (nW m^-2 sr^-1) ² of the 3. 6 and 4. 5 m fluctuations on scales >100''. The signal on smaller scales is instead produced by undetected galaxies at low and intermediate redshifts. Albeit Compton-thick, at scales > 100'' DCBHs produce a CXB (0. 5-2 keV) -NIRB (4. 5 m) cross-correlation signal of 10^-11 erg s^-1 cm^-2 nW m^-2 sr^-1 slightly dependent on the specific value of the absorbing gas column (N ₇ 10^25 cm^-2) adopted and in agreement with the recent measurements by 2012arXiv1210. 5302C. At smaller scales the cross-correlation is dominated by the emission of high-mass X-ray binaries (HMXB) hosted by the same low-z, undetected galaxies accounting for small scale NIRB fluctuations. These results outline the great potential of the NIRB as a tool to investigate the nature of the first galaxies and black holes.
Yue et al. (Wed,) studied this question.