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Dr. Mathilde Jauzac

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University of KwaZulu-Natal
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"Gravitational Lensing Analysis of the 12 'high-redshift' MACS Galaxy Clusters"
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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.

Back to Spring 2013 Astrophysics Seminars
Received Jan 13, 2013