Very high energy gamma-rays and the Hubble parameter

International audienceA new method, based on the absorption of very high-energy gamma-rays by the cosmic infrared background, was developed to constrain the value of the Hubble constant. As this value is both fundamental for cosmology and still not very well measured, such alternative methods are mandatory. Our lower limit at 68% confidence level is H0>74 km/s/MPc, leading, when combined with the HST results, to H0 ~ 76 km/s/MPc. Interestingly, this value, which is significantly higher than the usually considered one, is in exact agreement with other independent approaches based on baryonic acoustic oscillations and X-ray data. Future data from HESS-2 and CTA should help improving those results and make our method very effective