Universe opacity and Type Ia supernova dimming

TL;DR

This paper explores universe opacity due to intergalactic dust as an alternative explanation for Type Ia supernova dimming, challenging the necessity of dark energy and accelerating expansion in cosmological models.

Contribution

It demonstrates that an opaque universe model can fit supernova data as well as the standard Lambda-CDM model, suggesting an alternative to dark energy.

Findings

Opaque universe model fits supernova data at z<1.4 as well as Lambda-CDM.

Optimal intergalactic opacity is estimated at 0.10 ± 0.03 Gpc^{-1}.

Intergalactic opacity is higher than previous independent estimates but still plausible.

Abstract

In this paper, I revoke a debate about an origin of Type Ia supernova (SN Ia) dimming. I argue that except for a commonly accepted accelerating expansion of the Universe, a conceivable alternative for explaining this observation is universe opacity caused by light extinction by intergalactic dust, even though it is commonly assumed that this effect is negligible. Using data of the Union2.1 SN Ia compilation, I find that the standard $\Lambda$CDM model and the opaque universe model fit the SN Ia measurements at redshifts $z < 1.4$ comparably well. The optimum solution for the opaque universe model is characterized by the B-band intergalactic opacity $\lambda_B = 0.10 \pm 0.03 \, \mathrm{Gpc}^{-1}$ and the Hubble constant $H_0 = 68.0 \pm 2.5 \, \mathrm{km\,s^{-1}\, Mpc^{-1}}$. The intergalactic opacity is higher than that obtained from independent observations but still within acceptable limits. This result emphasizes that the issue of the accelerating expansion of the Universe as the origin of the SN Ia dimming is not yet definitely resolved. Obviously, the opaque universe model as an alternative to the $\Lambda$CDM model is attractive, because it avoids puzzles and controversies associated with dark energy and the accelerating expansion.