http://arxiv.org/abs/1907.10965
The attenuation produced by extragalactic background light (EBL) in $\gamma$-ray spectra of blazars has been used to constrain the Hubble constant ($H_0$) and matter density ($\Omega_{\rm m}$) of the Universe. We propose to estimate $H_0$ and $\Omega_{\rm m}$ using the well measured $>$10 GeV extragalactic $\gamma$-ray background (EGB). This suggestion is based on the facts that the $>$10 GeV EGB is totally explained by the emissions from blazars, and an EBL-absorption cutoff occurs at $\sim$50 GeV in the EGB spectrum. We fit the $>$10 GeV EGB data with modeled EGB spectrum. This results in $H_0=64.9^{+4.6}{-4.3}\rm \ km\ s^{-1}\ Mpc^{-1}$ and $\Omega{\rm m}=0.31^{+0.13}{-0.14}$. Note that the uncertainties may be underestimated due to the limit of our realization for EBL model.
$H_0$ and $\Omega{\rm m}$ are degenerate in our method.
Independent determination of $\Omega_{\rm m}$ by other methods would improve the constraint on $H_0$.
H. Zeng and D. Yan
Fri, 26 Jul 19
69/84
Comments: Accepted by ApJ
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