Very high energy gamma-rays and the Hubble parameter

TL;DR

This paper introduces a novel method using gamma-ray absorption to estimate the Hubble constant, yielding results consistent with other independent measurements and promising for future observational improvements.

Contribution

The paper proposes a new approach based on gamma-ray absorption by the cosmic infrared background to constrain the Hubble constant, providing an alternative to traditional methods.

Findings

Lower limit H0 > 74 km/s/Mpc at 68% confidence

Estimated H0 ~ 76 km/s/Mpc aligning with other methods

Future data from HESS-2 and CTA will refine results

Abstract

A new method, based on the absorption of very high-energy gamma-rays by the cosmic infrared background, is proposed to constrain the value of the Hubble constant. As this value is both fundamental for cosmology and still not very well measured, it is worth developing such alternative methods. Our lower limit at the 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 measurements. Forthcoming data from the experiments HESS-2 and CTA should help improving those results. Finally, we briefly mention a plausible correlation between absorption by the extragalactic background light and the absence of observation of gamma-ray bursts (GRBs) at very high energies.