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Please use this identifier to cite or link to this item: http://hdl.handle.net/1860/1915

Title: Weak lensing ellipticities in a strong lensing regime
Authors: Goldberg, David
Massey, Richard
Keywords: Gravitational Lensing
Issue Date: 11-Sep-2007
Publisher: American Astronomical Society
Citation: Astrophysical Journal
Abstract: It is now routine to measure the weak gravitational lensing shear signal from the mean ellipticity of distant galaxies. However, conversion between ellipticity and shear assumes local linearity of the lensing potential (i.e. that the spatial derivatives of the shear are small), and this condition is not satisfied in some of the most interesting regions of the sky. We extend a derivation of lensing equations to include higher order terms, and assess the level of biases introduced by assuming that first-order weak lensing theory holds in a relatively strong shear regime. We find that, even in a worst-case scenario, a fully linear analysis is accurate to within 1% outside ∼ 1.07 times the Einstein radius of a lens. The effect should therefore have little impact on measurements of overall cluster masses for the foreseeable future. However, at the level of accuracy demanded by upcoming lensing surveys, such biases ought to be considered in measurements of the inner slope of cluster mass distributions and the small-scale end of the mass power spectrum. Both of these are central in determining the relationship between baryonic and dark matter.
URI: http://arxiv.org/abs/0709.1479v1
Appears in Collections:Faculty Research and Publications (Physics)

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