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Title: Practical Weak-lensing Shear Measurement with Metacalibration

We report that metacalibration is a recently introduced method to accurately measure weak gravitational lensing shear using only the available imaging data, without need for prior information about galaxy properties or calibration from simulations. The method involves distorting the image with a small known shear, and calculating the response of a shear estimator to that applied shear. The method was shown to be accurate in moderate-sized simulations with galaxy images that had relatively high signal-to-noise ratios, and without significant selection effects. In this work we introduce a formalism to correct for both shear response and selection biases. We also observe that for images with relatively low signal-to-noise ratios, the correlated noise that arises during the metacalibration process results in significant bias, for which we develop a simple empirical correction. To test this formalism, we created large image simulations based on both parametric models and real galaxy images, including tests with realistic point-spread functions. We varied the point-spread function ellipticity at the five-percent level. In each simulation we applied a small few-percent shear to the galaxy images. We introduced additional challenges that arise in real data, such as detection thresholds, stellar contamination, and missing data. We applied cuts on the measuredmore » galaxy properties to induce significant selection effects. Finally, using our formalism, we recovered the input shear with an accuracy better than a part in a thousand in all cases.« less
Authors:
 [1] ;  [2]
  1. Brookhaven National Lab. (BNL), Upton, NY (United States)
  2. California Inst. of Technology (CalTech), Pasadena, CA (United States). Jet Propulsion Lab.
Publication Date:
Report Number(s):
BNL-114074-2017-JA
Journal ID: ISSN 1538-4357
Grant/Contract Number:
SC0012704
Type:
Accepted Manuscript
Journal Name:
The Astrophysical Journal (Online)
Additional Journal Information:
Journal Name: The Astrophysical Journal (Online); Journal Volume: 841; Journal Issue: 1; Journal ID: ISSN 1538-4357
Publisher:
Institute of Physics (IOP)
Research Org:
Brookhaven National Laboratory (BNL), Upton, NY (United States)
Sponsoring Org:
USDOE Office of Science (SC), High Energy Physics (HEP) (SC-25)
Country of Publication:
United States
Language:
English
Subject:
79 ASTRONOMY AND ASTROPHYSICS; cosmology: observations; gravitational lensing: weak; methods: observational
OSTI Identifier:
1376137

Sheldon, Erin S., and Huff, Eric M.. Practical Weak-lensing Shear Measurement with Metacalibration. United States: N. p., Web. doi:10.3847/1538-4357/aa704b.
Sheldon, Erin S., & Huff, Eric M.. Practical Weak-lensing Shear Measurement with Metacalibration. United States. doi:10.3847/1538-4357/aa704b.
Sheldon, Erin S., and Huff, Eric M.. 2017. "Practical Weak-lensing Shear Measurement with Metacalibration". United States. doi:10.3847/1538-4357/aa704b. https://www.osti.gov/servlets/purl/1376137.
@article{osti_1376137,
title = {Practical Weak-lensing Shear Measurement with Metacalibration},
author = {Sheldon, Erin S. and Huff, Eric M.},
abstractNote = {We report that metacalibration is a recently introduced method to accurately measure weak gravitational lensing shear using only the available imaging data, without need for prior information about galaxy properties or calibration from simulations. The method involves distorting the image with a small known shear, and calculating the response of a shear estimator to that applied shear. The method was shown to be accurate in moderate-sized simulations with galaxy images that had relatively high signal-to-noise ratios, and without significant selection effects. In this work we introduce a formalism to correct for both shear response and selection biases. We also observe that for images with relatively low signal-to-noise ratios, the correlated noise that arises during the metacalibration process results in significant bias, for which we develop a simple empirical correction. To test this formalism, we created large image simulations based on both parametric models and real galaxy images, including tests with realistic point-spread functions. We varied the point-spread function ellipticity at the five-percent level. In each simulation we applied a small few-percent shear to the galaxy images. We introduced additional challenges that arise in real data, such as detection thresholds, stellar contamination, and missing data. We applied cuts on the measured galaxy properties to induce significant selection effects. Finally, using our formalism, we recovered the input shear with an accuracy better than a part in a thousand in all cases.},
doi = {10.3847/1538-4357/aa704b},
journal = {The Astrophysical Journal (Online)},
number = 1,
volume = 841,
place = {United States},
year = {2017},
month = {5}
}