Extragalactic background light inferred from AEGIS galaxy SED-type fractions

TL;DR

This paper introduces a novel, data-driven method to derive the evolving spectrum of the extragalactic background light (EBL) from UV to mid-IR wavelengths, based on galaxy SED-type fractions across redshifts, with implications for gamma-ray attenuation.

Contribution

The study presents a new observationally based approach to determine the EBL spectrum evolution using galaxy SED-type fractions from redshift 0.2 to 1, including two extrapolation models for higher redshifts.

Findings

EBL is well constrained from UV to mid-IR, matching galaxy count data.

Uncertainties in the EBL model are quantified and discussed.

Implications for gamma-ray attenuation due to pair production are analyzed.

Abstract

The extragalactic background light (EBL) is of fundamental importance both for understanding the entire process of galaxy evolution and for gamma-ray astronomy. However, the overall spectrum of the EBL between 0.1 and 1000 microns has never been determined directly neither from observed luminosity functions (LFs), over a wide redshift range, nor from any multiwavelength observation of galaxy spectral energy distributions (SEDs). The evolving, overall spectrum of the EBL is derived here utilizing a novel method based on observations only. The changing fractions of quiescent galaxies, star-forming galaxies, starburst galaxies and active galactic nucleus (AGN) galaxies from redshift 0.2 to 1 are estimated, and two alternative extrapolations of SED types to higher redshifts are considered. This allows calculation of the evolving EBL. The EBL uncertainties in our modelling based directly on the data are quantified, and their consequences for attenuation of very-high-energy gamma-rays due to pair production on the EBL are discussed. It is concluded that the EBL seems well constrained from the UV to the mid-IR at an intensity level roughly matching galaxy count data. Independent efforts from IR and gamma-ray astronomy are needed in order to reduce the uncertainties in the far-IR.