A lower-limit flux for the extragalactic background light

Abstract

... A strict lower-limit flux for the evolving extragalactic background light (and in particular the cosmic infrared background) has been calculated up to redshift of 5. The computed flux is below the existing upper limits from direct observations, and in agreement with all existing limits derived from very-high energy gamma-ray observations. The corrected spectra are still in agreement with simple theoretical predictions. The derived strict lower-limit EBL flux is very close to the upper limits from gamma-ray observations. This is true for the present day EBL but also for the diffuse flux at higher redshift. If future detections of high redshift gamma-ray sources require a lower EBL flux than derived here, the physics assumptions used to derive the upper limits have to be revised. The lower-limit EBL model is not only needed for absorption features in AGN and other gamma-ray sources but is also essential when alternative particle processes are tested, which could prevent the high energy gamma-rays from being absorbed. It can also be used for a quaranteed interaction of cosmic-ray particles. The model is available online.