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Shape, shear and flexion: An analytic flexion formalism for realistic mass profiles

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posted on 2024-07-26, 14:13 authored by Paul D. Lasky, Christopher FlukeChristopher Fluke
Flexion is a non-linear gravitational lensing effect that arises from gradients in the convergence and shear across an image. We derive a formalism that describes non-linear gravitational lensing by a circularly symmetric lens in the thin-lens approximation. This provides us with relatively simple expressions for first- and second-flexion in terms of only the surface density and projected mass distribution of the lens. We give details of exact lens models, in particular providing flexion calculations for a Sersic-law profile, which has become increasingly popular over recent years. We further provide a single resource for the analytic forms of convergence, shear, first- and second-flexion for the following mass distributions: a point mass, singular isothermal sphere (SIS); Navarro-Frenk-White (NFW) profile; Sersic-law profile. We quantitatively compare these mass distributions and show that the convergence and first-flexion are better indicators of the Sersic shape parameter, while for the concentration of NFW profiles the shear and second-flexion terms are preferred.

Funding

The Commonwealth Cosmology Initiative: From the First Objects to the Cosmic Web

Australian Research Council

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PDF (Accepted manuscript)

ISSN

0035-8711

Journal title

Monthly Notices of the Royal Astronomical Society

Volume

396

Issue

4

Pagination

11 pp

Publisher

Wiley

Copyright statement

Copyright © 2009 The authors. Journal compilation Copyright © 2009 Royal Astronomical Society. The accepted manuscript is reproduced in accordance with the copyright policy of the publisher. The definitive publication is available at www.interscience.wiley.com.

Language

eng

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