CLASH: Complete Lensing Analysis of the Largest Cosmic Lens MACS J0717.5+3745 and Surrounding Structures

TL;DR

This paper presents a comprehensive weak and strong lensing analysis of the massive galaxy cluster MACS J0717.5+3745, revealing its detailed mass distribution and large-scale filamentary structure, and compares its mass to cosmological models.

Contribution

It provides the first combined weak and strong lensing mass profile of the largest known cosmic lens at z>0.5, including detailed modeling of its filamentary structure and comparison with LambdaCDM predictions.

Findings

Mass of the cluster is (2.8±0.4)×10^15 M_sun.

Weak and strong lensing data are consistent within 500 kpc/h.

Cluster mass is a 2σ outlier in LambdaCDM extreme value statistics.

Abstract

The galaxy cluster MACS J0717.5+3745 (z=0.55) is the largest known cosmic lens, with complex internal structures seen in deep X-ray, Sunyaev-Zel'dovich effect and dynamical observations. We perform a combined weak and strong lensing analysis with wide-field BVRi'z' Subaru/Suprime-Cam observations and 16-band Hubble Space Telescope observations taken as part of the Cluster Lensing And Supernova survey with Hubble (CLASH). We find consistent weak distortion and magnification measurements of background galaxies, and combine these signals to construct an optimally estimated radial mass profile of the cluster and its surrounding large-scale structure out to 5 Mpc/h. We find consistency between strong-lensing and weak-lensing in the region where these independent data overlap, <500 kpc/h. The two-dimensional weak-lensing map reveals a clear filamentary structure traced by distinct mass halos. We model the lensing shear field with 9 halos, including the main cluster, corresponding to mass peaks detected above 2.5\sigma_\kappa. The total mass of the cluster as determined by the different methods is M_{vir}=(2.8\pm0.4) \times 10^15 M_sun. Although this is the most massive cluster known at z>0.5, in terms of extreme value statistics we conclude that the mass of MACS J0717.5+3745 by itself is not in serious tension with LambdaCDM, representing only a ~2{\sigma} departure above the maximum simulated halo mass at this redshift.