CLUMP-3D: Three-dimensional Shape and Structure of 20 CLASH Galaxy Clusters from Combined Weak and Strong Lensing

We perform a three-dimensional triaxial analysis of 16 X-ray regular and 4 high-magnification galaxy clusters selected from the CLASH survey by combining two-dimensional weak-lensing and central strong-lensing constraints. In a Bayesian framework, we constrain the intrinsic structure and geometry of each individual cluster assuming a triaxial Navarro-Frenk-White halo with arbitrary orientations, characterized by the mass M-200c, halo concentration C-200c, and triaxial axis ratios (q(a) <= q(b)), and investigate scaling relations between these halo structural parameters. From triaxial modeling of the X-ray-selected subsample, we find that the halo concentration decreases with increasing cluster mass, with a mean concentration of C-200c = 4.82 +/- 0.30 at the pivot mass M-200c = 10(15)M(circle dot)h(-1). This is consistent with the result from spherical modeling, C-200c = 4.51 +/- 0.14. Independently of the priors, the minor-to-major axis ratio q(a) of our full sample exhibits a clear deviation from the spherical configuration (q(a) = 0.52 +/- 0.04 at 10(15)M(circle dot)h(-1) with uniform priors), with a weak dependence on the cluster mass. Combining all 20 clusters, we obtain a joint ensemble constraint on the minor-to-major axis ratio of q(a) = 0.652(-0.078)(+0.162) and a lower bound on the intermediate-to-major axis ratio of q(b) > 0.63 at the 2 sigma level from an analysis with uniform priors. Assuming priors on the axis ratios derived from numerical simulations, we constrain the degree of triaxiality for the full sample to be T= 0.79 +/- 0.03 at 10(15)M(circle dot)h(-1), indicating a preference for a prolate geometry of cluster halos. We find no statistical evidence for an orientation bias (f(geo) = 0.93 +/- 0.07), which is insensitive to the priors and in agreement with the theoretical expectation for the CLASH clusters.