SIMBAD references

The attenuation produced by extragalactic background light (EBL) in γ-ray spectra of blazars has been used to constrain the Hubble constant (H₀) and matter density (Ω_m) of the universe. We propose to estimate H₀ and Ω_m using the well-measured >10 GeV extragalactic γ-ray background (EGB). This suggestion is based on the fact that the >10 GeV EGB is totally explained by the emissions from blazars, and an EBL-absorption cutoff occurs at ∼50 GeV in the EGB spectrum. We fit the >10 GeV EGB data with modeled EGB spectrum. This results in H₀=64.9_–4.3^+4.6kms^–1Mpc^–1 and Ω_m=0.31_–0.14^+0.13. Note that the uncertainties may be underestimated due to the limit of our realization for EBL model. H₀ and Ω_m are degenerate in our method. Independent determination of Ω_m by other methods would improve the constraint on H₀.