We present γ-ray optical-depth calculations from a recently published
extragalactic background light (EBL) model built from multiwavelength galaxy
data from the Hubble Space Telescope Cosmic Assembly Near-Infrared Deep
Extragalactic Legacy Survey (HST/CANDELS). CANDELS gathers one of the deepest
and most complete observations of stellar and dust emissions in galaxies. This
model resulted in a robust derivation of the evolving EBL spectral energy
distribution up to z∼6, including the far-infrared peak. Therefore, the
optical depths derived from this model will be useful for determining the
attenuation of γ-ray photons coming from high-redshift sources, such as
those detected by the Large Area Telescope on board the Fermi Gamma-ray Space
Telescope, and for multi-TeV photons that will be detected from nearby sources
by the future Cherenkov Telescope Array. From these newly calculated optical
depths, we derive the cosmic γ-ray horizon and also measure the
expansion rate and matter content of the Universe including an assessment of
the impact of the EBL uncertainties. We find H0=61.9−2.4+2.9 km
s−1 Mpc−1 when fixing Ωm=0.32, and H0=65.6−5.0+5.6 km s−1 Mpc−1 and Ωm=0.19±0.07, when
exploring these two parameters simultaneously.Comment: 11 pages, 8 figures, 1 tables; Accepted by MNRA