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, Michael Hirsch

    Research output: Contribution to journalArticlepeer-review


    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. © 2012 The Authors.
    Original languageEnglish
    Pages (from-to)2711-2722
    Number of pages11
    JournalMonthly Notices of the Royal Astronomical Society
    Issue number4
    Publication statusPublished - 21 Dec 2012


    • Data analysis-methods
    • Gravitational lensing
    • Image processing-cosmology
    • Observations
    • Statistical-techniques
    • Weak-methods


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