Session 83 - Gravitational Lensing.
Display session, Friday, January 09
Exhibit Hall,

## [83.06] Weak Gravitational Lensing by Numerical Clusters

C. M. Oaxaca, T. G. Brainerd (Boston U.)

A current application of weak gravitational lensing is the determination of the masses of galaxy clusters from the shear pattern induced in the images of background galaxies. Observational techniques used to infer the cluster masses from weak lensing often invoke simplifying assumptions such as circular symmetry of the shear field and an isothermal cluster potential. Using high-resolution N-body simulations of the formation of massive clusters in a standard Cold Dark Matter universe, we will investigate the effect of these simplifying assumptions on the determination of the masses of z = 0.5 clusters.

A grid of 1002 \times 1002 light rays (corresponding to 200'' \times 200'') will be traced through each of the numerical clusters and the tangential shear that would be induced in the images of background galaxies will be determined directly. The cluster masses will then be inferred via a circular average of the tangential shear under the assumption of an isothermal cluster potential. These results will then be compared with the true masses of the clusters, known a priori from the simulations. Systematic trends in the inferred cluster masses will be investigated and quantified. Preliminary analysis suggests that under the above simplifications, cluster masses are underestimated by of order 30% on scales of 0.4 to 2.0 Mpc.