Heating of the intergalactic medium by primordial miniquasars

Saleem Zaroubi, Rajat M. Thomas, Naoshi Sugiyama, Joseph Silk

Research output: Contribution to journalArticlepeer-review


A simple analytical model is used to calculate the X-ray heating of the intergalactic medium (IGM) for a range of black hole masses. This process is efficient enough to decouple the spin temperature of the IGM from the cosmic microwave background (CMB) temperature and produce a differential brightness temperature of the order of ∼ 5-20 mK out to distances as large as a few comoving Mpc, depending on the redshift, black hole mass and lifetime. We explore the influence of two types of black holes, those with and without ionizing ultraviolet radiation. The results of the simple analytical model are compared to those of a full spherically symmetric radiative transfer code. Two simple scenarios are proposed for the formation and evolution of black hole mass density in the Universe. The first considers an intermediate mass black hole that form as an end-product of pop III stars, whereas the second considers supermassive black holes that form directly through the collapse of massive haloes with low spin parameter. These scenarios are shown not to violate any of the observational constraints, yet produce enough X-ray photons to decouple the spin temperature from that of the CMB. This is an important issue for future high-redshift 21-cm observations.

Original languageEnglish
Pages (from-to)1269-1279
Number of pages11
JournalMonthly Notices of the Royal Astronomical Society
Issue number4
StatePublished - Mar 2007
Externally publishedYes


  • Cosmology: theory
  • Diffuse radiation
  • Large-scale structure of Universe
  • Quasars: general
  • Radio lines: general


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