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Propagating residual biases in masked cosmic shear power spectra

Kitching, TD; Deshpande, AC; Taylor, PL; (2020) Propagating residual biases in masked cosmic shear power spectra. The Open Journal of Astrophysics , 3 10.21105/astro.2010.07749. Green open access

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Abstract

In this paper we derive a full expression for the propagation of weak lensing shape measurement biases into cosmic shear power spectra including the effect of missing data. We show using simulations that terms higher than first order in bias parameters can be ignored and the impact of biases can be captured by terms dependent only on the mean of the multiplicative bias field. We identify that the B-mode power contains information on the multiplicative bias. We find that without priors on the residual multiplicative bias $\delta m$ and stochastic ellipticity variance $\sigma_e$ that constraints on the amplitude of the cosmic shear power spectrum are completely degenerate, and that when applying priors the constrained amplitude $A$ is slightly biased low via a classic marginalisation paradox. Using all-sky Gaussian random field simulations we find that the combination of $(1+2\delta m)A$ is unbiased for a joint EE and BB power spectrum likelihood if the error and mean (precision and accuracy) of the stochastic ellipticity variance is known to better than $\sigma(\sigma_e)\leq 0.05$ and $\Delta\sigma_e\leq 0.01$, or the multiplicative bias is known to better than $\sigma(m)\leq 0.07$ and $\Delta m\leq 0.01$.

Type: Article
Title: Propagating residual biases in masked cosmic shear power spectra
Open access status: An open access version is available from UCL Discovery
DOI: 10.21105/astro.2010.07749
Publisher version: http://dx.doi.org/10.21105/astro.2010.07749
Language: English
Additional information: Article available under the Creative Commons Attribution 4.0 International (CC BY 4.0) licence
UCL classification: UCL
UCL > Provost and Vice Provost Offices
UCL > Provost and Vice Provost Offices > UCL BEAMS
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences > Dept of Space and Climate Physics
URI: https://discovery.ucl.ac.uk/id/eprint/10118591
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