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Abstract: We study the bias and scatter in mass measurements of galaxy clustersresulting from fitting a spherically-symmetric Navarro, Frenk and White model tothe reduced tangential shear profile measured in weak lensing observations. Thereduced shear profiles are generated for ~10^4 cluster-sized halos formed in aLCDM cosmological N-body simulation of a 1 Gpc-h box. In agreement withprevious studies, we find that the scatter in the weak lensing masses derivedusing this fitting method has irreducible contributions from the triaxialshapes of cluster-sized halos and uncorrelated large-scale matter projectionsalong the line-of-sight. Additionally, we find that correlated large-scalestructure within several virial radii of clusters contributes a smaller, butnevertheless significant, amount to the scatter. The intrinsic scatter due tothese physical sources is ~20% for massive clusters, and can be as high as ~30%for group-sized systems. For current, ground-based observations, however, thetotal scatter should be dominated by shape noise from the background galaxiesused to measure the shear. Importantly, we find that weak lensing massmeasurements can have a small, ~5%-10%, but non-negligible amount of bias.Given that weak lensing measurements of cluster masses are a powerful way tocalibrate cluster mass-observable relations for precision cosmologicalconstraints, we strongly emphasize that a robust calibration of the biasrequires detailed simulations which include more observational effects than weconsider here. Such a calibration exercise needs to be carried out for eachspecific weak lensing mass estimation method, as the details of the methoddetermine in part the expected scatter and bias. We present an iterative methodfor estimating mass M500c that can eliminate the bias for analyses ofground-based data.

Author: Matthew R. Becker, Andrey V. Kravtsov

Source: https://arxiv.org/

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