Testing Cosmic Opacity with the Combination of Strongly Lensed and Unlensed Supernova Ia

In this paper, we present a scheme to investigate the opacity of the universe in a cosmological-model-independent way, with the combination of current and future measurements of an SN Ia sample and galactic-scale strong gravitational lensing systems with SNe Ia acting as background sources. The observational data include the current newly compiled SNe Ia data (Pantheon sample) and a simulated sample of SNe Ia observed by the forthcoming Large Synoptic Survey Telescope (LSST), which are taken for luminosity distances (DL) possibly affected by the cosmic opacity, as well as strongly lensed SNe Ia observed by the LSST, which are responsible for providing the observed time-delay distance unaffected by the cosmic opacity. Focusing on only one specific type of standard cosmological probe, this provides an original method to measure cosmic opacity at high precision. Working on the simulated sample of strongly lensed SNe Ia observed by the LSST in the 10 yr z-band search, our results show that, with the combination of the current newly compiled SNe Ia data (Pantheon sample), there is no significant deviation from the transparency of the universe at the current observational data level. Moreover, strongly lensed SNe Ia in a 10 yr LSST z-band search would produce more robust constraints on the validity of cosmic transparency, with a larger sample of unlensed SNe Ia detected in the future LSST survey. We have also discussed the ways in which our methodology could be improved, with the combination of current and future available data in the gravitational wave and electromagnetic domain.