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

Understand

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.