A Strong Lensing Model of RCS1 J0224−0002.5

Abstract We present the details of a strong lensing model of RCS1 J0224−0002.5, a strong lensing cluster at z = 0.773, based on data from Hubble Space Telescope/WFC3, Advanced Camera for Surveys, and WFC2. Of particular interest in this field is a z = 4.8786 Ly α emitter (LAE), 15″ from the brightest cluster galaxy (BCG) that stretches northwest to west of the BCG in three different images, with a fourth counter-image ∼4″ southeast of the BCG. Using methods consistent with those used in studying five other LAEs in A. Navarre et al., we find that the cluster is best modeled by two cluster-scale dark matter halos aligned nearly perpendicular to each other at the center of the cluster. A z = 2.396 source is also lensed with six images, providing several constraints that were instrumental in producing this model.