Energy Injection And Absorption In The Cosmic Dark Ages
  Dark matter annihilation or de-excitation, decay of metastable species, or
other new physics may inject energetic electrons and photons into the
photon-baryon fluid during and after recombination. As such particles cool,
they partition their energy into a large number of efficiently ionizing
electrons and photons, which in turn modify the ionization history. Recent work
has provided a simple method for constraining arbitrary energy deposition
histories using the cosmic microwave background (CMB); in this note, we present
results describing the energy deposition histories for photons and electrons as
a function of initial energy and injection redshift. With these results, the
CMB bounds on any process injecting some arbitrary spectrum of electrons,
positrons and/or photons with arbitrary redshift dependence can be immediately
computed.
