Fermi Large Area Telescope Constraints on the Gamma-ray

A.A. Abdo, M. Ackermann, M. Ajello, A. Allafort, W.B. Atwood, L. Baldini, J. Ballet, J. Granot, M. Ziegler

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130 Citations (Scopus)
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The Extragalactic Background Light (EBL) includes photons with wavelengths from ultraviolet to infrared, which are effective at attenuating gamma rays with energy above ~10 GeV during propagation from sources at cosmological distances. This results in a redshift- and energy-dependent attenuation of the gamma-ray flux of extragalactic sources such as blazars and Gamma-Ray Bursts (GRBs). The Large Area Telescope onboard Fermi detects a sample of gamma-ray blazars with redshift up to z~3, and GRBs with redshift up to z~4.3. Using photons above 10 GeV collected by Fermi over more than one year of observations for these sources, we investigate the effect of gamma-ray flux attenuation by the EBL. We place upper limits on the gamma-ray opacity of the Universe at various energies and redshifts, and compare this with predictions from well-known EBL models. We find that an EBL intensity in the optical-ultraviolet wavelengths as great as predicted by the "baseline" model of Stecker et al. (2006) can be ruled out with high confidence.
Original languageEnglish
Pages (from-to)1082-1096
JournalThe Astrophysical Journal
Issue number2
Publication statusPublished - 2010


  • diffuse radiation
  • dust, extinction
  • gamma rays: general
  • opacity
  • galaxies: active
  • gamma-ray burst: general


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