LoCuSS: Subaru Weak Lensing Study of 30 Galaxy Clusters

Abstract

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 $\le z \le$ 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 6$\ \sigma$ and 11$\ \sigma$, respectively, for low ($M_{\rm vir}\lt$ 6 $\times$ 10$^{14}\ h^{-1}\ M_\odot$) and high ($M_{\rm vir} \gt $ 6 $\times$ 10$^{14}\ h^{-1}\ M_\odot$) 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 ($c_{\rm vir}$) decreases with increasing cluster mass ($M_{\rm vir}$). The best-fit $c_{\rm vir}$–$M_{\rm vir}$ relation is: $c_{\rm vir}$($M_{\rm vir}$) $=$ 8.75$^{+4.13}_{-2.89} \times$ ($M_{\rm vir}/$10$^{14}\ h^{-1}\ M_\odot$)$^{-\alpha}$ with $\alpha \approx$ 0.40$\ \pm\ $0.19: i.e., a non-zero slope is detected at 2$\ \sigma$ significance. This relation gives a concentration of $c_{\rm vir} =$ 3.48$^{+1.65}_{-1.15}$ for clusters with $M_{\rm vir} =$ 10$^{15}\ h^{-1}M_\odot$, which is inconsistent at 4$\ \sigma$ significance with the values of $c_{\rm vir} \sim$ 10 reported for strong-lensing-selected clusters. We have found that the measurement error on the cluster mass is smaller at higher over-densities, $\Delta \simeq$ 500–2000, than at the virial over-density, $\Delta_{\rm vir} \simeq$ 110; typical fractional errors at $\Delta \simeq$ 500–2000 are improved to $\ \sigma$($M_\Delta$)$/M_{\Delta } \simeq$ 0.1–0.2 compared with 0.2–0.3 at $\Delta_{\rm vir}$. Furthermore, comparing the 3D spherical mass with the 2D cylinder mass, obtained from the aperture mass method at a given aperture radius, $\theta_\Delta$, reveals $M_{\rm 2D}$($\lt \theta_{\Delta}$)$/M_{\rm 3D}$($\lt r_\Delta = D_{\rm l}\theta_{\Delta}$) $\simeq$ 1.46 and 1.32 for $\Delta =$ 500 and $\Delta_{\rm vir}$, 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.