A New Way to Measure How Much Light Has Been Produced Since the Universe was Born

Abstract

The extragalactic background light (EBL) that permeates the Universe in the optical-IR is very closely connected to the galaxy/ large scale structure formation in our Universe. Unfortunately, measuring the EBL has been proven very difficult, for very simple reasons that I will discuss in the first part of my talk. Luckily, we found a parameter-free way to break the deadlock of measuring the EBL with Fermi, NASA’s new Gamma-ray satellite, observations of the lobes of nearby radio galaxies. Our method measures the energy density of the Cosmic Infrared Background at the location of radio galaxies by using Fermi Gamma-ray and multiwavelength observations of their radio lobes. We present an application of our method for the well-studied radio galaxy Fornax A, showing that Fermi observations will provide us with a direct, model independent measurement of the Cosmic Infrared Background.