A New Measurement of the Hubble Constant and Matter Content of the Universe Using Extragalactic Background Light γ-Ray Attenuation

The Hubble constant H <SUB>0</SUB> and matter density Ω<SUB> m </SUB> 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}<SUB>0</SUB>={67.4}<SUB>-6.2</SUB><SUP>+6.0</SUP> km s<SUP>−1</SUP> Mpc<SUP>−1</SUP> and {{{Ω }}}<SUB>m</SUB>={0.14}<SUB>-0.07</SUB><SUP>+0.06</SUP>. 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 <SUB>0</SUB> = 66.6 ± 1.6 km s<SUP>−1</SUP> Mpc<SUP>−1</SUP> and Ω<SUB> m </SUB> = 0.29 ± 0.02.