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Weak gravitational shear and flexion with polar shapelets

Massey, Richard and Rowe, Barnaby and Refregier, Alexandre and Bacon, David J. and Bergé, Joel (2007) Weak gravitational shear and flexion with polar shapelets. Monthly Notices of the Royal Astronomical Society, 380 (1). pp. 229-245. ISSN 0035-8711. doi:10.1111/j.1365-2966.2007.12072.x.

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We derive expressions, in terms of 'polar shapelets', for the image distortion operations associated with weak gravitational lensing. Shear causes galaxy shapes to become elongated, and is sensitive to the second derivative of the projected gravitational potential along their line of sight; flexion bends galaxy shapes into arcs, and is sensitive to the third derivative. Polar shapelets provide a natural representation, in which both shear and flexion transformations are compact. Through this tool, we understand progress in several weak lensing methods. We then exploit various symmetries of shapelets to construct a range of shear estimators with useful properties. Through an analogous investigation, we also explore several flexion estimators. In particular, some of the estimators can be measured simultaneously and independently for every galaxy, and will provide unique checks for systematics in future weak lensing analyses. Using simulated images from the Shear TEsting Programme, we show that we can recover input shears with no significant bias. A complete software package to parametrize astronomical images in terms of polar shapelets, and to perform a full weak lensing analysis, is available on the Internet.

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Additional Information:© 2007 The Authors. Journal compilation © 2007 RAS. Accepted 2007 June 4. Received 2007 May 1; in original form 2006 September 28. The authors are pleased to thank Richard Ellis, Gary Bernstein, Sarah Bridle, Mandeep Gill, Dave Goldberg, Catherine Heymans, John Irwin, Mike Jarvis, Reiko Nakajima, Jason Rhodes, Nick Scoville, Marina Shmakova and Lisa Wright for their help. DJB is supported by a PPARC Advanced Fellowship.
Funding AgencyGrant Number
PPARC Advanced FellowshipUNSPECIFIED
Subject Keywords:gravitational lensing; data analysis; image processing techniques
Issue or Number:1
Record Number:CaltechAUTHORS:MASmnras07
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:11354
Deposited By: Tony Diaz
Deposited On:08 Aug 2008 23:21
Last Modified:08 Nov 2021 21:57

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