GeV gamma-ray attenuation and the high-redshift UV background

Rudy C. Gilmore, Piero Madau, Joel R. Primack, Rachel S. Somerville, Francesco Haardt

Research output: Contribution to journalArticlepeer-review

148 Scopus citations


We present new calculations of the evolving UV background out to the epoch of cosmological reionization and make predictions for the amount of GeV gamma-ray attenuation by electron-positron pair production. Our results are based on recent semi-analytic models of galaxy formation, which provide predictions of the dust-extinguished UV radiation field due to starlight, and empirical estimates of the contribution due to quasars. We account for the reprocessing of ionizing photons by the intergalactic medium. We test whether our models can reproduce estimates of the ionizing background at high redshift from flux decrement analysis and proximity effect measurements from quasar spectra, and identify a range of models that can satisfy these constraints. Pair production against soft diffuse photons leads to a spectral cut-off feature for gamma rays observed between 10 and 100 GeV. This cut-off varies with redshift and the assumed star formation and quasar evolution models. We find only negligible amounts of absorption for gamma rays observed below 10 GeV for any emission redshift. With observations of high-redshift sources in sufficient numbers by the Fermi Gamma-ray Space Telescope and new ground-based instruments, it should be possible to constrain the extragalactic background light in the UV and optical portion of the spectrum.

Original languageEnglish (US)
Pages (from-to)1694-1708
Number of pages15
JournalMonthly Notices of the Royal Astronomical Society
Issue number4
StatePublished - Nov 2009
Externally publishedYes

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science


  • Cosmology: theory
  • Diffuse radiation
  • Gamma rays: bursts
  • Gamma rays: theory
  • Intergalactic medium
  • Ultraviolet: galaxies


Dive into the research topics of 'GeV gamma-ray attenuation and the high-redshift UV background'. Together they form a unique fingerprint.

Cite this