Practical Weak-lensing Shear Measurement with Metacalibration

By Erin Sheldon, E. Huff. 2017

161 citations recorded by the source corpus.

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. Using our formalism, we recovered the input shear with an accuracy better than a part in a thousand in all cases.

Subfields: Astronomy and Astrophysics, Atomic and Molecular Physics, and Optics, Computer Vision and Pattern Recognition

View Paper: https://www.semanticscholar.org/paper/8a1685883d7d9d99b7587b9b8849f42f94d040cc

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Citations in the corpus

Dark Energy Survey Year 1 results: weak lensing shape catalogues (2017, methodology): “Metacalibration is described in detail in Huff & Mandelbaum (2017) and Sheldon & Huff (2017), hereafter SH17.”
Cosmological constraints from cosmic shear two-point correlation functions with HSC survey first-year data (2019, methodology): “…would be important to explore other missing redshift-dependent selection biases by using techniques such as metacalibration (Huff & Mandelbaum 2017; Sheldon & Huff 2017), and it would be also important to implement more advanced methods of accounting for baryonic feedback effects such as one…”
Dark Energy Survey Year 1 Results: The Photometric Data Set for Cosmology (2017, methodology): “We used the ngmix18 code (Sheldon 2014; Sheldon & Huff 2017; Jarvis et al. 2016) to reanalyze pixel-level data from multi-epoch postage stamps of each object in the Y1A1 GOLD coadd catalog.”
Dark Energy Survey Year 1 Results: redshift distributions of the weak-lensing source galaxies (2017, methodology): “The primary shear catalogue for DES Y1 is produced by the METACALIBRATION algorithm (Huff & Mandelbaum 2017; Sheldon & Huff 2017), and a secondary catalogue using IM3SHAPE (Zuntz et al. 2013) is used as a cross-check.”
The first-year shear catalog of the Subaru Hyper Suprime-Cam Subaru Strategic Program Survey (2017, methodology): “In general, these basic mathematical issues in estimating shear from per-galaxy shapes require either external calibration using simulations, or some form of selfcalibration (e.g., Fenech Conti et al. 2017; Huff & Mandelbaum 2017; Sheldon & Huff 2017).”
Dark Energy Survey Year 1 results: weak lensing mass calibration of redMaPPer galaxy clusters (2018, methodology): “The use of two different photometric estimators is necessary because when calculating the selection response, the internal photometry of the METACALIBRATION, with measurements on sheared images, must be used for all selection and weighting of sources.”
The Dark Energy Survey Image Processing Pipeline (2018, methodology): “We then perform improved photometric and morphological measurement with multi-epoch, multi-object fitting (MOF; Drlica-Wagner et al. 2017), and Metacalibration (Metacal; Sheldon & Huff 2017), a technique to accurately measure weak gravitational lensing shear.”