A Lower-Limit Flux for the Extragalactic Background Light

TL;DR

This paper establishes a strict lower-limit flux for the extragalactic background light up to redshift 5, aligning with existing gamma-ray constraints and serving as a baseline for future high-energy astrophysics studies.

Contribution

It introduces a new lower-limit EBL flux model that is consistent with all current observational constraints and is useful for gamma-ray and cosmic-ray physics analyses.

Findings

Lower-limit EBL flux is below existing upper limits.

The flux aligns with gamma-ray observational constraints.

The model is available online for community use.

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.