Constraints on the Extragalactic Background Light from Very High Energy Gamma-Ray Observations of Blazars

TL;DR

This paper uses gamma-ray observations of blazars to set upper limits on the extragalactic background light, providing constraints that are consistent with some measurements but challenge certain models.

Contribution

It introduces a simple, model-independent technique to constrain the EBL using VHE gamma-ray data from blazars.

Findings

Constraints are consistent with some EBL measurements.

Results marginally challenge several EBL models.

Technique has well-defined errors and is independent of EBL models.

Abstract

The extragalactic background light (EBL) from the infrared to the ultraviolet is difficult to measure directly, but can be constrained with a variety of methods. EBL photons absorb gamma-rays from distant blazars, allowing one to use blazar spectra from atmospheric Cherenkov telescopes (ACTs) to put upper limits on the EBL by assuming a blazar source spectrum. Here we apply a simple technique, similar to the one developed by Schroedter (2005), to the most recent very-high energy (VHE) gamma-ray observations of blazars to put upper limits on the EBL energy density. This technique is independent of the EBL model and has well-defined errors on the constraints. Our results are consistent with EBL measurements and constraints but marginally inconsistent with several EBL models.