Extensive surveys with the Hubble Space Telescope ( HST ) over the past decade , targeting some of most massive clusters in the sky , have uncovered dozens of galaxy-cluster strong lenses .
The massive cluster strong-lens scale is typically \theta _ { E } \sim 10 \arcsec to \sim 30 - 35 \arcsec , with only a handful of clusters known with Einstein radii \theta _ { E } \sim 40 \arcsec or above ( for a source at z _ { s } \sim 2 , nominally ) .
Here we report another very large cluster lens , RXC J0032.1+1808 ( at z = 0.3956 ) , the second richest cluster in the redMapper cluster catalog and the 85th most massive cluster in the Planck Sunyaev-Zel ’ dovich catalog .
With both our Light-Traces-Mass and fully parametric ( dPIEeNFW ) approaches , we construct strong lensing models based on 18 multiple images of 5 background galaxies in the HST data from the Reionization Lensing Cluster Survey ( RELICS ; using also data also from a previous snapshot program ) , in addition to a previously found sextuply imaged system in this cluster .
Furthermore , we compare these models to the Lenstool and GLAFIC models , which were produced independently as part of the RELICS program .
All models reveal a large effective Einstein radius of \theta _ { E } \simeq 40 \arcsec ( z _ { s } = 2 ) .
The central region of the cluster shows an obvious concentration of substructures , which together account for the large critical area .
Although RXC J0032.1+1808 has a very large critical area and lensing strength , only three magnified high-redshift candidates are found within the field targeted by RELICS .
Nevertheless , given its exceptional lensing strength , we expect many more high-redshift candidates will be seen in an additional coverage with HST , and in deeper , longer-wavelength observations with JWST .