Astronomy and Astrophysics – Astronomy
Scientific paper
Jan 2010
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2010aas...21543602c&link_type=abstract
American Astronomical Society, AAS Meeting #215, #436.02; Bulletin of the American Astronomical Society, Vol. 42, p.384
Astronomy and Astrophysics
Astronomy
Scientific paper
Third-order weak gravitational lensing, or flexion, is an extension to the standard weak lensing formalism accounting for variation in the gravitational shear across a single background galaxy image. Since flexion is a third-order effect, it can only be effectively measured in regions where the lensing convergence is non-negligible compared to unity. This means that the distinction between the true, physical shear and the measurable, reduced shear is non-trivial, and therefore any measurement of flexion must consider the mass-sheet degeneracy and its effect on both the measurable shear and flexion fields. We introduce a new technique for weak lensing flexion measurement. Instead of measuring shapelet coefficients or surface brightness moments, we instead fit an analytic surface brightness profile. We assume that the (unobservable) unlensed galaxy profile is well described by an elliptical Gaussian, and we parametrize the lensed image profile with a coordinate transformation which is entirely invariant to the mass-sheet degeneracy. We apply this technique to simulated galaxy cluster data images as a proof of concept, as well as to archival Hubble space telescope images of the Abell 1689.
Bautz Marshall
Cain Benjamin
Schechter Paul
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