Radiative Transfer in a Clumpy Universe. III. The Nature of Cosmological Ionizing Sources

  title={Radiative Transfer in a Clumpy Universe. III. The Nature of Cosmological Ionizing Sources},
  author={Piero Madau and Francesco Haardt and Martin J. Rees},
  journal={The Astrophysical Journal},
The history of the transition from a neutral intergalactic medium (IGM) to one that is almost fully ionized can reveal the character of cosmological ionizing sources. We study the evolution of the volume filling factors of H II and He III regions in a clumpy IGM and discuss the implications for rival reionization scenarios of the rapid decline observed at z3 in the space density of optical and radio-loud quasars and of the large population of star-forming galaxies recently discovered at the… 

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