分类： 天文学 >> 天文学 提交时间： 2023-02-19
Rachel Mandelbaum
Barnaby Rowe
James Bosch
Chihway Chang
Frederic Courbin
Mandeep Gill
Mike Jarvis
Arun Kannawadi
Tomasz Kacprzak
Claire Lackner
Alexie Leauthaud
Hironao Miyatake
Reiko Nakajima
Jason Rhodes
Melanie Simet
Joe Zuntz
Bob Armstrong
Sarah Bridle
Jean Coupon
Jörg P. Dietrich
摘要： The GRavitational lEnsing Accuracy Testing 3 (GREAT3) challenge is the third in a series of image analysis challenges, with a goal of testing and facilitating the development of methods for analyzing astronomical images that will be used to measure weak gravitational lensing. This measurement requires extremely precise estimation of very small galaxy shape distortions, in the presence of far larger intrinsic galaxy shapes and distortions due to the blurring kernel caused by the atmosphere, telescope optics, and instrumental effects. The GREAT3 challenge is posed to the astronomy, machine learning, and statistics communities, and includes tests of three specific effects that are of immediate relevance to upcoming weak lensing surveys, two of which have never been tested in a community challenge before. These effects include realistically complex galaxy models based on high-resolution imaging from space; spatially varying, physically-motivated blurring kernel; and combination of multiple different exposures. To facilitate entry by people new to the field, and for use as a diagnostic tool, the simulation software for the challenge is publicly available, though the exact parameters used for the challenge are blinded. Sample scripts to analyze the challenge data using existing methods will also be provided. See http://great3challenge.info and http://great3.projects.phys.ucl.ac.uk/leaderboard/ for more information.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
Rachel Mandelbaum
Barnaby Rowe
Robert Armstrong
Deborah Bard
Emmanuel Bertin
James Bosch
Dominique Boutigny
Frederic Courbin
William A. Dawson
Annamaria Donnarumma
Ian Fenech Conti
Raphael Gavazzi
Marc Gentile
Mandeep S. S. Gill
David W. Hogg
Eric M. Huff
M. James Jee
Tomasz Kacprzak
Martin Kilbinger
Thibault Kuntzer
摘要： 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 S\'{e}rsic 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.
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