Measurement of the expansion rate of the Universe from \gamma-ray attenuation

Understand

A measurement of the expansion rate of the Universe (that is the Hubble constant, H0) is derived here using the gamma-ray attenuation observed in the spectra of gamma-ray sources produced by the interaction of extragalactic gamma-ray photons with the photons of the extragalactic background light (EBL).

• The Hubble constant that is determined with our technique, for a Lambda CDM cosmology, is H0=71.8_{-5.6}^{+4.6}(stat)_{-13.8}^{+7.2}(syst) km s^{-1} Mpc^{-1}.
• This value is compatible with present-day measurements using well established methods such as local distance ladders and cosmological probes.
• The recent detection of the cosmic gamma-ray horizon (CGRH) from multiwavelength observation of blazars, together with the advances in the knowledge of the EBL, allow us to measure the expansion rate of the Universe.