Twist and Turn: Weak Lensing Image Distortions to Second Order

Abstract

We account for all the image distortions relevant to weak gravitational lensing to second order. Besides the familiar shear, convergence, rotation and flexions, we find a new image distortion with two distinct descriptions, the twist and the turn. Like rotation, this distortion is not activated gravitationally to first order, but will be activated by systematic effects. We examine the rotational properties of twist and turn, and their effect on images in real and shapelet space. We construct estimators for the new distortion, taking into account the centroid shift which it generates. We then use these estimators to make first constraints on twist using the STAGES HST survey; we find that the mean twist estimator is consistent with zero. We measure correlation functions for our twist estimator on the survey, again finding no evidence of systematic effects.

9 pages, 9 figures. Accepted by MNRAS; expands discussion of distortions and estimators

References in corpus (5)

• The dark matter environment of the Abell 901/902 supercluster: a weak lensing analysis of the HST STAGES survey
• STAGES: the Space Telescope A901/2 Galaxy Evolution Survey
• Weak lensing goes bananas: What flexion really measures
• Weak gravitational shear and flexion with polar shapelets
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Cited by in corpus (14)

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• The dark matter of gravitational lensing
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• Generalised model-independent characterisation of strong gravitational lenses IV: formalism-intrinsic degeneracies
• Gravitational Flexion by Elliptical Dark Matter Haloes
• On the validity of the Born approximation for weak cosmic flexions
• A numerical study of the effects of primordial non-Gaussianities on weak lensing statistics
• Raytracing simulations of coupled dark energy models
• 3D weak lensing with spin wavelets on the ball
• Shape, shear and flexion II - Quantifying the flexion formalism for extended sources with the ray-bundle method
• Generalised model-independent characterisation of strong gravitational lenses VII: impact of source properties and higher-order lens properties on the local lens reconstruction
• Weak Lensing Mass Reconstruction: Flexion vs Shear
• The general theory of secondary weak gravitational lensing
• A short review on joint weak and strong cluster lens-mass reconstruction