Weak gravitational shear and flexion with polar shapelets
Abstract
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.
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.Attached Files
Published - MASmnras07.pdf
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Additional details
- Eprint ID
- 11354
- Resolver ID
- CaltechAUTHORS:MASmnras07
- PPARC Advanced Fellowship
- Created
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2008-08-08Created from EPrint's datestamp field
- Updated
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2021-11-08Created from EPrint's last_modified field