In Jauzac et al. (2012), we presented the weak gravitational lensing analysis of MACSJ0717.5+3745, an X-ray luminous cluster, at a redshift of z ~0.55. This cluster is part of the high-z MACS subsample, 12 galaxy clusters et z > 0.5. By making a weak gravitational lensing analysis of MACSJ0717 and its outskirts, we were able to report the weak-lensing detection of a large-scale filament which funnels the matter into the core of the cluster. Our analysis is based on a mosaic of 18 HST/ACS maps, i.e. an area of ~10x20 arcmin2. To test the consistency of our weak lensign analysis, we first compared our results with the strong lensing analysis of Limousin et al. (2012, A&A) of the cluster core. The weak and strong lensing density profiles of the cluster core showed a really good agreement. In terms of mass integrated in a radius of 500 kpc (given the same center), the strong lensing gives 1.06+/-0.03 1e15 Msun, while the weak lensing gives 1.04+/-0.008 1e15 Msun. The excellent agreement between both values and density profiles confirms the strength of our weak lensing analysis. Our analysis detects the MACSJ0717 filament within the 3 sigma detection contour of the lensing mass reconstruction, and underlines the importance of filaments for theoretical and numerical models of the mass distribution in the Cosmic Web.
Using the mass modeling method presented in Jauzac et al. (2012), we extended the study to the whole high-z sample. Thanks to the multi-wavelength dataset available for these clusters, we are able to obtain strongly constrained mass models for all of them. The multi-wavelength analysis of massive galaxy clusters is one of the most efficient way to study the different distant galaxy populations observed thanks to the natural amplification provided by these massive objects, and also provides a unique way to constrain the cluster mass distribution. Thanks to a relevant modeling of the cluster mass distributions, we derive as a function of redshift (from 0.5 to 0.7), the mass profiles, the total mass, and the fraction of substructures. As this last quantity is a function of the redshift, and is tracing the mass assembly, its measurement gives information on the evolution of the mass assembly in galaxy clusters. Therefore, the direct comparison of these results with simulations will put constraints on models of cluster evolution.
Received Jan 13, 2013