Constraints on the Optical-IR extragalactic background from gamma-ray absorption studies

Understand

Very high energy (VHE) gamma-rays from extragalactic sources, interacting by gamma-gamma collisions with diffuse intergalactic radiation fields, provide an alternative way to constrain the diffuse background light, completely independent of direct measurements.

• The limits depend however on our knowledge of the physics of the gamma-ray sources.
• After clarifying the interplay between background light and VHE spectra, I summarize the extent and validity of the obtainable limits, and where future improvements can be expected.