Analytical Weak-lensing Shear Responses of Galaxy Properties and Galaxy Detection

Abstract

Shear estimation bias from galaxy detection and blending identification is now recognized as an issue for ongoing and future weak lensing surveys. Currently, the empirical approach to correcting for this bias involves numerically shearing every observed galaxy and rerunning the detection and selection process. In this work, we provide an analytical correction for this bias that is accurate to subpercent level and far simpler to use. With the interpretation that smoothed image pixel values and galaxy properties are projections of the image signal onto a set of basis functions, we analytically derive the linear shear responses of both the pixel values and the galaxy properties (i.e., magnitude, size and shape) using the shear responses of the basis functions. With these derived shear responses, we correct for biases from shear-dependent galaxy detection and galaxy sample selection. With the analytical covariance matrix of measurement errors caused by image noise on pixel values and galaxy properties, we correct for the noise biases in galaxy shape measurement and the detection/selection process to the second-order in noise. The code used for this paper can carry out the detection, selection, and shear measurement for ~1000 galaxies per CPU second. The algorithm is tested with realistic image simulations, and we find, after the analytical correction (without relying on external image calibration) for the detection/selection bias of about $-4\%$, the multiplicative shear bias is $-0.12\pm 0.10\%$ for isolated galaxies; and $-0.3\pm 0.1\%$ for blended galaxies with Hyper Suprime-Cam observational condition.

23 pages, 22 figures, Accepted in MNRAS

References in corpus (7)

• Array Programming with NumPy
• The Shear TEsting Programme 2: Factors affecting high precision weak lensing analyses
• Measuring the Cosmic Shear in Fourier Space
• Impact of Atmospheric Chromatic Effects on Weak Lensing Measurements
• Noise from Undetected Sources in Dark Energy Survey Images
• Quantum yield and charge diffusion in the Nancy Grace Roman Space Telescope infrared detectors
• Cosmic Shear Measurement using Autoconvolved Images

Cited by in corpus (13)

• A General Framework for Removing Point Spread Function Additive Systematics in Cosmological Weak Lensing Analysis
• Simulating image coaddition with the Nancy Grace Roman Space Telescope: I. Simulation methodology and general results
• A Differentiable Perturbation-based Weak Lensing Shear Estimator
• Forklens: Accurate weak-lensing shear measurement with deep learning
• Dark Energy Survey Year 6 Results: Cell-based Coadds and Metadetection Weak Lensing Shape Catalogue
• Chromatic Effects on the PSF and Shear Measurement for the Roman Space Telescope High-Latitude Wide Area Survey
• Analysis of biasing from noise from the Nancy Grace Roman Space Telescope: implications for weak lensing
• Simulating image coaddition with the Nancy Grace Roman Space Telescope: II. Analysis of the simulated images and implications for weak lensing
• Simulating image coaddition with the Nancy Grace Roman Space Telescope: III. Software improvements and new linear algebra strategies
• Analytical Noise Bias Correction for Precise Weak Lensing Shear Inference
• Optimizing the Roman Space Telescope High-Latitude Wide Area Survey for mitigating chromatic PSF effects on shear measurement
• D${}_4$CNN$\times$AnaCal: Physics-Informed Machine Learning for Accurate and Precise Weak Lensing Shear Estimation
• Emulating redshift mixing due to blending in weak gravitational lensing