Measurement of the Extragalactic Background Light Spectral Energy Distribution with VERITAS

Abstract

The extragalactic background light (EBL), a diffuse photon field in the optical and infrared range, is a record of radiative processes over the universe’s history. Spectral measurements of blazars at very high energies (>100 GeV) enable the reconstruction of the spectral energy distribution (SED) of the EBL, as the blazar spectra are modified by redshift- and energy-dependent interactions of the gamma-ray photons with the EBL. The spectra of 14 VERITAS-detected blazars are included in a new measurement of the EBL SED that is independent of EBL SED models. The resulting SED covers an EBL wavelength range of 0.56–56 μ m, and is in good agreement with lower limits obtained by assuming that the EBL is entirely due to radiation from cataloged galaxies.