Spectral analysis of Fermi-LAT blazars above 50 GeV

Understand

We present an analysis of the intrinsic (unattenuated by the extragalactic background light, EBL) power-law spectral indices of 128 extragalactic sources detected up to z~2 with the Fermi-Large Area Telescope (LAT) at very high energies (VHEs, E>50 GeV).

• The median of the intrinsic index distribution is 2.20 (versus 2.54 for the observed distribution).
• We also analyze the observed spectral breaks (i.e., the difference between the VHE and high energy, HE, 100 MeV<E<300 GeV, spectral indices).
• The LAT has now provided a large sample of sources detected both at VHE and HE with comparable exposure that allows us to test models of extragalactic gamma-ray photon propagation.