A Determination of the Intergalactic Redshift Dependent UV-Optical-NIR Photon Density Using Deep Galaxy Survey Data and the Gamma-ray Opacity of the Universe

TL;DR

This paper empirically determines the intergalactic background light across redshifts using galaxy survey data and assesses the universe's gamma-ray opacity without relying on theoretical assumptions.

Contribution

It provides an observationally based, empirical calculation of the intergalactic photon density and gamma-ray opacity, reducing reliance on theoretical models.

Findings

Derived redshift-dependent photon density of the IBL

Placed observational limits on gamma-ray universe opacity

Compared results with Fermi telescope measurements

Abstract

We calculate the intensity and photon spectrum of the intergalactic background light (IBL) as a function of redshift using an approach based on observational data obtained in many different wavelength bands from local to deep galaxy surveys. This allows us to obtain an empirical determination of the IBL and to quantify its observationally based uncertainties. Using our results on the IBL, we then place 68% confidence upper and lower limits on the opacity of the universe to gamma-rays, free of the theoretical assumptions that were needed for past calculations. We compare our results with measurements of the extragalactic background light and upper limits obtained from observations made by the Fermi Gamma-ray Space Telescope.