Illuminating the dark ages: Cosmic backgrounds from accretion onto
  primordial black hole dark matter
  Cold dark matter as the sum of different mass Primordial Black Holes (PBH)
can explain a number of unsolved astrophysical mysteries. Here I assume a broad
PBH mass distribution providing the bulk of the dark matter, consistent with
all constraints and estimate the baryon accretion onto PBH contributing to
cosmic background radiations, mainly the correlation signal between the Cosmic
X-ray and the Cosmic infrared background fluctuations in deep Chandra and
Spitzer surveys. I assume Bondi capture and advection dominated disk accretion
with reasonable baryon densities and effective relative velocities between
baryons and PBH, as well as appropriate accretion and radiation efficiencies,
and integrate over the PBH mass spectrum and cosmic time. The X-ray
contribution is indeed consistent with the residual X-ray background signal and
the X-ray/infrared fluctuations. The flux peaks at z~17-30, consistent with
constraints requiring the signal to come from high redshifts. The PBH
contribution to the infrared background fluctuations is only about 1%.
  Magnetic fields are an essential ingredient in the Bondi capture process, and
PBH can play a role in amplifying early seed fields and maintaining them until
the galactic dynamo processes set in. The contribution of the assumed PBH
population to the re-ionization history of the universe does not conflict with
the Planck ionization limits. X-ray heating from PBH can provide a contribution
to the entropy floor in groups of galaxies. The tantalizing EDGES redshifted
21-cm absorption line feature can be connected to the radio contribution to the
cosmic background radiation. Finally, the number of intermediate-mass black
holes and the diffuse X-ray emission in the Galactic Center are consistent with
the assumed PBH dark matter. Some of the discrete sources in the deepest
Chandra observations of the Galactic Ridge could indeed be accreting PBH.
