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

Kacprzak, Tomasz and Zuntz, Joe and Rowe, Barnaby and Bridle, Sarah and Refregier, Alexandre and Amara, Adam and Voigt, Lisa and Hirsch, Michael (2012) Measurement and calibration of noise bias in weak lensing galaxy shape estimation. Monthly Notices of the Royal Astronomical Society, 427 (4). pp. 2711-2722. ISSN 0035-8711.

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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.

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Additional Information:© 2012 The Authors. Monthly Notices of the Royal Astronomical Society © 2012 RAS. Accepted 2012 June 28. Received 2012 June 22; in original form 2012 March 28. Article first published online: 26 Nov. 2012. TK, SB, MH, BR and JZ acknowledge support from the European Research Council in the form of a Starting Grant with number 240672. Part of BR’s work was done at the Jet Propulsion Laboratory, California Institute of Technology, under contract with NASA. We thank Gary Bernstein for suggesting the calibration approach and for many fruitful discussions. We acknowledge the use of the UCL Legion High Performance Computing Facility, and associated support services, in the completion of this work. We thank Dugan Witherick for help with Legion Cluster. We also thank Mike Jarvis, Catherine Heymans, Cris Sabiu and Caroline Pung for helpful discussions.
Funding AgencyGrant Number
European Research Council Starting Grant240672
Subject Keywords:gravitational lensing: weak; methods: data analysis; methods: statistical; techniques: image processing; cosmology: observations
Issue or Number:4
Record Number:CaltechAUTHORS:20130116-093049069
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Official Citation:Kacprzak, T., Zuntz, J., Rowe, B., Bridle, S., Refregier, A., Amara, A., Voigt, L. and Hirsch, M. (2012), Measurement and calibration of noise bias in weak lensing galaxy shape estimation. Monthly Notices of the Royal Astronomical Society, 427: 2711–2722. doi: 10.1111/j.1365-2966.2012.21622.x
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:36419
Deposited By: Tony Diaz
Deposited On:17 Jan 2013 22:31
Last Modified:03 Oct 2019 04:38

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