Mitigating the effects of undersampling in weak lensing shear estimation with metacalibration

Monthly Notices of the Royal Astronomical Society, vol. 502, pp. 4048–4063

Abstract

ABSTRACT metacalibration is a state-of-the-art technique for measuring weak gravitational lensing shear from well-sampled galaxy images. We investigate the accuracy of shear measured with metacalibration from fitting elliptical Gaussians to undersampled galaxy images. In this case, metacalibration introduces aliasing effects leading to an ensemble multiplicative shear bias about 0.01 for Euclid and even larger for the Roman Space Telescope, well exceeding the missions’ requirements. We find that this aliasing bias can be mitigated by computing shapes from weighted moments with wider Gaussians as weight functions, thereby trading bias for a slight increase in variance of the measurements. We show that this approach is robust to the point-spread function in consideration and meets the stringent requirements of Euclid for galaxies with moderate to high signal-to-noise ratios. We therefore advocate metacalibration as a viable shear measurement option for weak lensing from upcoming space missions.

Authors 3

1. Arun Kannawadi corresponding Aachen Leiden Observatory

   Leiden University · Princeton University · Leiden Observatory

   Affiliation as printed

   Department of Astrophysical Sciences, Princeton University, 4 Ivy Lane, Princeton, NJ 08544, USA

   Leiden Observatory, Leiden University, PO Box 9513, NL-2300 RA Leiden, the Netherlands

2. Erik Rosenberg

   University of Cambridge

   Affiliation as printed

   Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge CB3 0HA, UK

3. Henk Hoekstra Aachen Leiden Observatory

   Leiden University · Leiden Observatory

   Affiliation as printed

   Leiden Observatory, Leiden University, PO Box 9513, NL-2300 RA Leiden, the Netherlands