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Abstract: Weak gravitational lensing has been used extensively in the past decade toconstrain the masses of galaxy clusters, and is the most promisingobservational technique for providing the mass calibration necessary forprecision cosmology with clusters. There are several challenges in estimatingcluster masses, particularly a the sensitivity to astrophysical effects andobservational systematics that modify the signal relative to the theoreticalexpectations, and b biases that can arise due to assumptions in the massestimation method, such as the assumed radial profile of the cluster. All ofthese challenges are more problematic in the inner regions of the cluster,suggesting that their influence would ideally be suppressed for the purpose ofmass estimation. However, at any given radius the differential surface densitymeasured by lensing is sensitive to all mass within that radius, and thecorrupted signal from the inner parts is spread out to all scales. We develop anew statistic that is ideal for estimation of cluster masses because itcompletely eliminates mass contributions below a chosen scale which we suggestshould be about 20 per cent of the virial radius, and thus reduces sensitivityto systematic and astrophysical effects. We use simulated and analyticalprofiles to quantify systematic biases on the estimated masses for severalstandard methods of mass estimation, finding that these can lead to significantmass biases that range from ten to over fifty per cent. The mass uncertaintieswhen using our new statistic are reduced by up to a factor of ten relative tothe standard methods, while only moderately increasing the statistical errors.This new method of mass estimation will enable a higher level of precision infuture science work with weak lensing mass estimates for galaxy clusters.

Autor: Rachel Mandelbaum, Uros Seljak, Tobias Baldauf, Robert E. Smith


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