paper

The Clustering of Undetected High-redshift Black Holes and Their Signatures in Cosmic Backgrounds

arXiv:1907.03675 · doi:10.1093/mnras/stz1891

Abstract

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\sim 2-3, we find that such models produce a poor fit to the observed fluctuations while simultaneously overproducing the local black hole mass density. Additionally, we rule out the hypothesis of a missing Galactic foreground of warm dust that produces coherent fluctuations in the X-ray via reflection of Galactic X-ray binary emission. Although we firmly rule out accreting massive black holes as the source of these missing fluctuations, additional studies will be required to determine their origin.

NOTE: Version 1 of this manuscript (accepted for publication 7/8/19) contained an error in section 5.2 which led to the incorrect conclusion that coherent X-ray fluctuations could be plausibly explained by reflected Galactic X-ray emission. Version 2 (amended and re-accepted for publication 7/24/19) fixes this error. 19 pages, 14 figures

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