Journal Article

Measurement and calibration of noise bias in weak lensing galaxy shape estimation

Tomasz Kacprzak, Joe Zuntz, Barnaby Rowe, Sarah Bridle, Alexandre Refregier, Adam Amara, Lisa Voigt and Michael Hirsch

in Monthly Notices of the Royal Astronomical Society

Published on behalf of The Royal Astronomical Society

Volume 427, issue 4, pages 2711-2722
Published in print December 2012 | ISSN: 0035-8711
Published online December 2012 | e-ISSN: 1365-2966 | DOI:
Measurement and calibration of noise bias in weak lensing galaxy shape estimation

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Weak gravitational lensing has the potential to constrain cosmological parameters to high precision. However, as shown by the Shear Testing Programmes and Gravitational lensing Accuracy Testing challenges, measuring galaxy shears is a non-trivial task: various methods introduce different systematic biases which have to be accounted for. We investigate how pixel noise on the image affects the bias on shear estimates from a maximum likelihood forward model-fitting approach using a sum of co-elliptical Sérsic profiles, in complement to the theoretical approach of an associated paper. We evaluate the bias using a simple but realistic galaxy model and find that the effects of noise alone can cause biases of the order of 1–10 per cent on measured shears, which is significant for current and future lensing surveys. We evaluate a simulation-based calibration method to create a bias model as a function of galaxy properties and observing conditions. This model is then used to correct the simulated measurements. We demonstrate that, for the simple case in which the correct range of galaxy models is used in the fit, the calibration method can reduce noise bias to the level required for estimating cosmic shear in upcoming lensing surveys.

Keywords: gravitational lensing: weak; methods: data analysis; methods: statistical; techniques: image processing; cosmology: observations

Journal Article.  8001 words.  Illustrated.

Subjects: Astronomy and Astrophysics

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