GREAT3 results I: systematic errors in shear estimation and the impact of real galaxy morphology
Creators: name: Mandelbaum, Rachel
name: Rowe, Barnaby
name: Armstrong, Robert
name: Bard, Deborah
name: Bertin, Emmanuel
name: Bosch, James
name: Boutigny, Dominique
name: Courbin, Frederic
name: Dawson, William A.
name: Donnarumma, Annamaria
name: Conti, Ian Fenech
name: Gavazzi, Raphael
name: Gentile, Marc
name: Gill, Mandeep S. S.
name: Hogg, David W.
name: Huff, Eric M.
name: Jee, M. James
name: Kacprzak, Tomasz
name: Kilbinger, Martin
name: Kuntzer, Thibault
name: Lang, Dustin
name: Luo, Wentao
name: March, Marisa C.
name: Marshall, Philip J.
name: Meyers, Joshua E.
name: Miller, Lance
name: Miyatake, Hironao
name: Nakajima, Reiko
name: Mboula, Fred Maurice Ngole
name: Nurbaeva, Guldariya
name: Okura, Yuki
name: Paulin-Henriksson, Stephane
name: Rhodes, Jason
name: Schneider, Michael D.
name: Shan, Huanyuan
name: Sheldon, Erin S.
name: Simet, Melanie
name: Starck, Jean-Luc
name: Sureau, Florent
name: Tewes, Malte
name: Adami, Kristian Zarb
name: Zhang, Jun
name: Zuntz, Joe
Publisher: name: arXiv
Year: 2014
Subjects: subject: Cosmology and Nongalactic Astrophysics (astro-ph.CO)
subject: FOS: Physical sciences
subject: FOS: Physical sciences

description: We present first results from the third GRavitational lEnsing Accuracy Testing (GREAT3) challenge, the third in a sequence of challenges for testing methods of inferring weak gravitational lensing shear distortions from simulated galaxy images. GREAT3 was divided into experiments to test three specific questions, and included simulated space- and ground-based data with constant or cosmologically-varying shear fields. The simplest (control) experiment included parametric galaxies with a realistic distribution of signal-to-noise, size, and ellipticity, and a complex point spread function (PSF). The other experiments tested the additional impact of realistic galaxy morphology, multiple exposure imaging, and the uncertainty about a spatially-varying PSF; the last two questions will be explored in Paper II. The 24 participating teams competed to estimate lensing shears to within systematic error tolerances for upcoming Stage-IV dark energy surveys, making 1525 submissions overall. GREAT3 saw considerable variety and innovation in the types of methods applied. Several teams now meet or exceed the targets in many of the tests conducted (to within the statistical errors). We conclude that the presence of realistic galaxy morphology in simulations changes shear calibration biases by $\sim 1$ per cent for a wide range of methods. Other effects such as truncation biases due to finite galaxy postage stamps, and the impact of galaxy type as measured by the Sérsic index, are quantified for the first time. Our results generalize previous studies regarding sensitivities to galaxy size and signal-to-noise, and to PSF properties such as seeing and defocus. Almost all methods' results support the simple model in which additive shear biases depend linearly on PSF ellipticity.
description: 32 pages + 15 pages of technical appendices; 28 figures; published in MNRAS; all data and other information may be found at https://github.com/barnabytprowe/great3-public as the GREAT3 website and leaderboard are no longer live. v3 has updates to this comment only