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 NavarroFrenkWhite 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 10¹⁵ M 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 10¹⁵ M 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 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 10¹⁵ M 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.