分类： 天文学 >> 天文学 提交时间： 2023-02-19
Mohamed M. Shaaban
Ajay S. Gill
Jacqueline McCleary
Richard J. Massey
Steven J. Benton
Anthony M. Brown
Christopher J. Damaren
Tim Eifler
Aurelien A. Fraisse
Spencer Everett
Mathew N. Galloway
Michael Henderson
Bradley Holder
Eric M. Huff
Mathilde Jauzac
William C. Jones
David Lagattuta
Jason Leung
Lun Li
Thuy Vy T. Luu Johanna M. Nagy
摘要： The statistical power of weak lensing measurements is principally driven by the number of high redshift galaxies whose shapes are resolved. Conventional wisdom and physical intuition suggest this is optimised by deep imaging at long (red or near IR) wavelengths, to avoid losing redshifted Balmer break and Lyman break galaxies. We use the synthetic Emission Line EL-COSMOS catalogue to simulate lensing observations using different filters, from various altitudes. Here were predict the number of exposures to achieve a target z > 0.3 source density, using off-the-shelf and custom filters. Ground-based observations are easily better at red wavelengths, as (more narrowly) are space-based observations. However, we find that SuperBIT, a diffraction-limited observatory operating in the stratosphere, should instead perform its lensing-quality observations at blue wavelengths.
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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