LoCuSS: Subaru Weak Lensing Study of 30 Galaxy Clusters

We use high-quality Subaru/Suprime-Cam imaging data to conduct a detailed weak lensing study of the distribution of dark matter in a sample of 30 X-ray luminous galaxy clusters at 0.15 ≤ z ≤ 0.3. A weak lensing signal is detected at high statistical significance in each cluster, the total signal-to-noise ratio of the detections ranging from 5 to 13. Comparing spherical models to the tangential distortion profiles of the clusters individually, we are unable to discriminate statistically between a singular isothermal sphere (SIS) and Navarro, Frenk, and White (NFW) models. However, when the tangential distortion profiles are combined and then models are fitted to the stacked profile, the SIS model is rejected at 6σ and 11σ, respectively, for low (M_vir < 6 × 10¹⁴h^-1M_odot) and high (M_vir > 6 × 10¹⁴h^-1M_odot) mass bins. We also used individual cluster NFW model fits to investigate the relationship between the cluster mass and the concentration, finding that the concentration (c_vir) decreases with increasing cluster mass (M_vir). The best-fit c_vir-M_vir relation is: c_vir(M_vir) = 8.75^+4.13_-2.89 × (M_vir/10¹⁴h^-1M_odot)^-α with α≈0.40±0.19: i.e., a non-zero slope is detected at 2σ significance. This relation gives a concentration of c_vir = 3.48^+1.65_-1.15 for clusters with M_vir = 10¹⁵h^-1M_odot, which is inconsistent at 4σ significance with the values of c_vir ∼ 10 reported for strong-lensing-selected clusters. We have found that the measurement error on the cluster mass is smaller at higher over-densities, Δ ≃ 500-2000, than at the virial over-density, Δ_vir ≃ 110; typical fractional errors at Δ ≃ 500-2000 are improved to σ(M_Δ)/M_Δ ≃ 0.1-0.2 compared with 0.2-0.3 at Δ_vir. Furthermore, comparing the 3D spherical mass with the 2D cylinder mass, obtained from the aperture mass method at a given aperture radius, θ_Δ, reveals M_2D(<θ_Δ)/M_3D (<r_Δ = D₁θ_Δ) ≃ 1.46 and 1.32 for Δ = 500 and Δ_vir, respectively. The amplitude of this offset agrees well with that predicted by integrating an NFW model of cluster-scale halos along the line-of-sight.