Brightest Cluster Galaxies in Strongly-Lensing Galaxy Clusters and Richness- and Redshift-Matched Samples

We present a statistical analysis of 588 strongly-lensing galaxy clusters and groups, selected from publicly-available imaging sky surveys primarily by the COOL-LAMPS (ChicagO Optically selected strong Lenses — Located At the Margins of Public Surveys) collaboration. The foreground lenses are found at photometric redshifts 0.2 < z < 1.2. Using photometric methods, we compare this extensive sample of hundreds of strong-lensing systems to a sample of non-lensing systems that are matched in redshift and galaxy richness. Previous work on SDSS data has suggested that the luminosity of a cluster’s brightest cluster galaxy (BCG) may be related to its lensing potential, in that lensing BCGs are significantly brighter than non-lensing counterparts in an otherwise matched sample. We independently confirm this trend using DECaLS data and a custom redshift- and richness-estimation pipeline, and find that lensing BCGs tend to have a 27.0% larger half-light radius than non-lensing BCGs. We additionally find that lensing clusters tend to be more centrally concentrated in projection along the line-of-sight than non-lensing clusters matched in larger richness apertures. This effect is unlikely to be caused by cluster orientation bias alone. We find no evidence of ellipticity differences in the sample BCGs, but do find marginally-significant differences in positions of the BCGs versus the second brightest cluster members