Searching for an EBL attenuation signature in the Fermi/LAT 1st year catalog data

TL;DR

This study investigates whether the Fermi/LAT 1st year gamma-ray data shows signs of attenuation caused by the Extragalactic Background Light, aiming to better understand the density of UV to optical cosmic photons.

Contribution

It explores the potential of large high-energy gamma-ray datasets to detect EBL attenuation signatures and compares observational results with theoretical EBL models.

Findings

No clear EBL attenuation signature detected in the data

Current sensitivity limits hinder detection of attenuation effects

Future data improvements may enable detection of EBL signatures

Abstract

Observations of distant sources of high-energy (HE) gamma-rays are affected by attenuation resulting from the interaction of the gamma-rays with low energy photons from the diffuse meta-galactic radiation fields at ultraviolet (UV) to infrared (IR) wavelengths (Extragalactic Background Light; EBL). Recently, a large data-set of HE observations from the 1st year survey of the Large Area Telescope (LAT) instrument on-board of the Fermi satellite became available, covering an energy range from 100 MeV up to 100 GeV. In this paper, the potential of such large HE data-sets to probe the density of the EBL - especially in the UV to optical - is explored. The data from the catalog is investigated for an attenuation signature in the energy range 10-100 GeV and the results are compared with the predictions from EBL model calculations. No clear signature is found. The statistics are still limited by (1) the sensitivity of Fermi/LAT to detect sources above 10 GeV, (2) the number of firmly identified sources with known redshift, both which will improve over the coming years.