Observations of quasar reddening demonstrate that extinction by dust in the intergalactic medium is significant at optical wavelengths, but the impact of this extinction on the spectral intensity of the extragalactic background light (EBL) has not yet been assessed in a quantitative way. We use an interstellar dust extinction model of Weingartner and Draine and combine this with simple but physically reasonable expressions for dust evolution to arrive at an intergalactic dust model with two adjustable parameters. The resulting opacities closely match observational constraints from Imara and Loeb at near-optical wavelengths. We convolve this intergalactic dust model with a simple EBL model (described elsewhere in this meeting) to determine that optical EBL intensity is reduced by approximately 3% due to intergalactic dust. The "missing" light is of course shifted to longer wavelengths. Nevertheless, this result is a partial vindication for H.W.M. Olbers and his predecessor, J.P.L. de Cheseaux, who were the first to speculate that an absorbing medium might help to explain the darkness of the night sky.
American Astronomical Society Meeting Abstracts #233
- Pub Date:
- January 2019