Caustic and Weak-Lensing Estimators of Galaxy Cluster Masses

There are only two methods for estimating the mass distribution in the outer regions of galaxy clusters, where virial equilibrium does not hold: weak gravitational lensing and identification of caustics in redshift space. For the first time, we apply both methods to three clusters: Abell 2390, MS 1358.4+6245, and Cl 0024+1654. The two measures are in remarkably good agreement out to ~2 h -1 Mpc from the cluster centers. This result demonstrates that the caustic technique is a valuable complement to weak lensing. With a few tens of redshifts per square comoving megaparsec within the cluster, the caustic method is applicable for any z ≲ 0.5.