2019ApJ...885..137D

The Hubble constant H₀ 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 H₀=67.4_–6.2^+6.0 km s^–1 Mpc^–1 and Ω_m=0.14_–0.07^+0.06. 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 H₀ = 66.6 ± 1.6 km s^–1 Mpc^–1 and Ω_m = 0.29 ± 0.02.