RELICS: A Strong Lens Model for SPT-CLJ0615-5746, a z=0.972 Cluster

Abstract

We present a lens model for the cluster SPT-CLJ0615$-$5746, which is the highest redshift ($z=0.972$) system in the Reionization of Lensing Clusters Survey (RELICS), making it the highest redshift cluster for which a full strong lens model is published. We identify three systems of multiply-imaged lensed galaxies, two of which we spectroscopically confirm at $z=1.358$ and $z=4.013$, which we use as constraints for the model. We find a foreground structure at $z\sim 0.4$, which we include as a second cluster-sized halo in one of our models; however two different statistical tests find the best-fit model consists of one cluster-sized halo combined with three individually optimized galaxy-sized halos, as well as contributions from the cluster galaxies themselves. We find the total projected mass density within $r=26.7"$ (the region where the strong lensing constraints exist) to be $M=2.51_{-0.09}^{+0.15}\times 10^{14}$~M${}_{\odot }$. If we extrapolate out to $r_{500}$, our projected mass density is consistent with the mass inferred from weak lensing and from the Sunyaev-Zel'dovich effect ($M\sim 10^{15}$~M${}_{\odot }$). This cluster is lensing a previously reported $z\sim 10$ galaxy, which, if spectroscopically confirmed, will be the highest-redshift strongly lensed galaxy known.

15 pages, 8 figures 4 tables. ApJ Accepted