A new measurement of the Hubble constant and matter content of the universe using extragalactic background light γ-ray attenuation

Abstract

The Hubble constant H 0 and matter density Ω m of the universe are measured using the latest γ-ray attenuation results from Fermi-LAT and Cerenkov telescopes. This methodology is based upon the fact that the extragalactic background light supplies opacity for very high energy photons via photon–photon interaction. The amount of γ-ray attenuation along the line of sight depends on the expansion rate and matter content of the universe. This novel strategy results in a value of H_(0)=67.4^(+6.0)_(-6.2) km s− 1 Mpc− 1 and Ω_(m) = 0.14^(+0.06)_(-0.07). These estimates are independent and complementary to those based on the distance ladder, cosmic microwave background (CMB), clustering with weak lensing, and strong lensing data. We also produce a joint likelihood analysis of our results from γ-rays and those from more mature methodologies, excluding the CMB, yielding a combined value of H_(0) = 66.6 ± 1.6 km s^(−1) Mpc^(−1) and Ω_(m)= 0.29 ± 0.02.