We explore the possibility that the gravitational waves (GWs) detected in 2015 were strongly-lensed by massive galaxy clusters. We estimate that the odds on one of the GWs being strongly-lensed is $10^5:1$, taking in to account the binary black hole merger rate, the gravitational optics of known cluster lenses, and the star formation history of the universe. It is therefore very unlikely, but not impossible that one of the GWs was strongly-lensed. We identify three spectroscopically confirmed cluster strong lenses within the 90% credible sky localisations of the three GWs. Moreover, the GW credible regions intersect the disk of the Milky Way, behind which undiscovered strong galaxy cluster lenses may reside. We therefore use well constrained mass models of the three clusters within the credible regions and three further example clusters to predict that half of the putative next appearances of the GWs would be detectable by LIGO, and that they would arrive at Earth within three years of first detection.
|Number of pages||6|
|Journal||Royal Astronomical Society. Monthly Notices|
|Early online date||11 Jan 2018|
|Publication status||Published - Apr 2018|
Bibliographical note5 pages, 2 figures, submitted to MNRAS Letters