Gamma Rays to Probe the Extragalactic Background Light

Roger Grau Haro


The Extragalactic Background Light (EBL) is the accumulated light produced throughout the universe's history across the whole electromagnetic spectrum, mostly by stars (directly or re-processed by dust). As EBL is faint compared to diffuse foregrounds like e.g. zodiacal light, direct measurements of its total intensity (beyond the contribution of resolved discrete sources) are challenging. One way of measuring the EBL is using Very High Energy (VHE) photons coming from sources at cosmological distances. VHE photons can interact with the EBL and produce electron-positron pairs, a process that can be detected as an absorption in the observed gamma-ray spectrum. This method requires assumptions on the intrinsic spectrum of the source. Through the use of Monte Carlo simulations, and archival data of the MAGIC telescopes, we have studied the impact that the assumptions so far adopted in the literature have in the estimates of the EBL density, and how the use of more generic ones would modify the results.