Effects of spatial fluctuations in the extragalactic background light on hard gamma-ray spectra

Kudoda, A.M.
Faltenbacher, A.
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Oxford University Press (OUP)
This study investigates the impact of the fluctuations in the extragalactic background light (EBL) on the attenuation of the hard gamma-ray spectra of distant blazars. EBL fluctuations occur on the scales up to 100 Mpc and are caused by the clustering of galaxies. The EBL photons interact with high-energy gamma-rays via the electron-positron pair production mechanism: gamma + gamma '-> e(+) + e(-). The attenuation of gamma-rays depends on their energy and the density of the intervening EBL photon field. Using a simple model for the evolution of the mean EBL photon density, we implement an analytical description of the EBL fluctuations. We find that the amplitudes of the EBL energy density can vary by +/- 1 per cent as a function of environment. The EBL fluctuations lead to mild alterations of the optical depth or equivalently the transmissivity for gamma-rays from distant blazars. Our model predicts maximum changes of +/- 10 per cent in the gamma-ray transmissivity. However, this translates into marginal differences in the power-law slopes of currently observed gamma-ray spectra. The slopes of deabsorbed gamma-ray spectra differ by not more than +/- 1 per cent if EBL fluctuations are included.
Stars: formation, Stars: fundamental parameters, Stars: luminosity function, Mass function, Dust, extinction, Diffuse radiation, GALAXY REDSHIFT SURVEY, MU-M, STAR-FORMATION, COSMIC LIGHT, DEEP FIELD, COBE DIRBE, UNIVERSE, EMISSION
Kudoda, A.M. and Faltenbacher, A. Effects of spatial fluctuations in the extragalactic background light on hard gamma-ray spectra. Monthly Notices of the Royal Astronomical Society, 467(3), pp. 2896-2902.