The clustering of undetected high-redshift black holes and their signatures in cosmic backgrounds

Angelo Ricarte, Fabio Pacucci, Nico Cappelluti, Priyamvada Natarajan

Research output: Contribution to journalArticlepeer-review

5 Scopus citations


There exist hitherto unexplained fluctuations in the cosmic infrared background on arcminute scales and larger. These have been shown to cross-correlate with the cosmic X-ray background, 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 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.

Original languageEnglish (US)
Pages (from-to)1006-1022
Number of pages17
JournalMonthly Notices of the Royal Astronomical Society
Issue number1
StatePublished - Oct 11 2019


  • Black hole physics
  • Cosmic background radiation
  • Galaxies: active
  • Infrared: diffuse background
  • Quasars: general
  • X-rays: diffuse background

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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