http://arxiv.org/abs/1907.03675
There exist hitherto unexplained fluctuations in the Cosmic Infrared Background (CIB) on arcminute scales and larger. These have been shown to cross-correlate with the Cosmic X-ray Background (CXB), leading several authors to attribute the excess to a high-redshift growing black hole population. In order to investigate potential sources that could explain this excess, in this paper, we develop a new framework to compute the power spectrum of undetected sources that do not have constant flux as a function of halo mass. In this formulation, we combine a semi-analytic model for black hole growth and their simulated spectra from hydrodynamical simulations. Revisiting the possible contribution of a high-redshift black hole population, we find that too much black hole growth is required at early epochs for z>6 accretion to explain these fluctuations. Examining a population of accreting black holes at more moderate redshifts, z~2-3, we find that such models are also unable to produce a reasonable fit to the observed fluctuations. We show that the data instead highly prefer a simple power law with P proportional to q^-1.5 for the implicated sources. We speculate that a new Galactic foreground of warm dust may exhibit such behaviour, and the cross-correlation with CXB could be attributed to reflected light from Galactic X-ray binaries. While we firmly rule out accreting massive black holes as the source of these missing fluctuations, additional tests will be required to determine their origin.
A. Ricarte, F. Pacucci, N. Cappelluti, et. al.
Tue, 9 Jul 19
22/81
Comments: 19 pages, 14 figures, accepted by MNRAS 7/8/19
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