Practical Weaklensing Shear Measurement with Metacalibration
Abstract
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 moderatesized simulations with galaxy images that had relatively high signaltonoise 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 signaltonoise 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 pointspread functions. We varied the pointspread function ellipticity at the fivepercent level. In each simulation we applied a small fewpercent 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 »
 Authors:
 Brookhaven National Lab. (BNL), Upton, NY (United States)
 California Inst. of Technology (CalTech), Pasadena, CA (United States). Jet Propulsion Lab.
 Publication Date:
 Research Org.:
 Brookhaven National Laboratory (BNL), Upton, NY (United States)
 Sponsoring Org.:
 USDOE Office of Science (SC), High Energy Physics (HEP) (SC25)
 OSTI Identifier:
 1376137
 Report Number(s):
 BNL1140742017JA
Journal ID: ISSN 15384357
 Grant/Contract Number:
 SC0012704
 Resource Type:
 Journal Article: 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 15384357
 Publisher:
 Institute of Physics (IOP)
 Country of Publication:
 United States
 Language:
 English
 Subject:
 79 ASTRONOMY AND ASTROPHYSICS; cosmology: observations; gravitational lensing: weak; methods: observational
Citation Formats
Sheldon, Erin S., and Huff, Eric M. Practical Weaklensing Shear Measurement with Metacalibration. United States: N. p., 2017.
Web. doi:10.3847/15384357/aa704b.
Sheldon, Erin S., & Huff, Eric M. Practical Weaklensing Shear Measurement with Metacalibration. United States. doi:10.3847/15384357/aa704b.
Sheldon, Erin S., and Huff, Eric M. 2017.
"Practical Weaklensing Shear Measurement with Metacalibration". United States.
doi:10.3847/15384357/aa704b.
@article{osti_1376137,
title = {Practical Weaklensing 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 moderatesized simulations with galaxy images that had relatively high signaltonoise 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 signaltonoise 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 pointspread functions. We varied the pointspread function ellipticity at the fivepercent level. In each simulation we applied a small fewpercent 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 = {10.3847/15384357/aa704b},
journal = {The Astrophysical Journal (Online)},
number = 1,
volume = 841,
place = {United States},
year = 2017,
month = 5
}

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 moderatesized simulations with galaxy images that had relatively high signaltonoise 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 imagesmore »

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