http://arxiv.org/abs/1508.05655
We demonstrate recovery of weak gravitational lensing shear at parts-per-thousand accuracy using an implementation of the Bayesian Fourier Domain (BFD) method proposed by Bernstein \& Armstrong (2014, BA14). The BFD formalism is rigorously correct for Nyquist-sampled, background-limited, uncrowded image of background galaxies. BFD does not assign shapes to galaxies, instead compressing the pixel data D into a vector of moments M, such that we have an analytic expression for the probability P(M|g) of obtaining the observations with gravitational lensing distortion g along the line of sight. We extend the BA14 formalism to include detection and selection of galaxies without inducing biases on the inferred g. We describe a practical algorithm for conducting BFD’s integrations over the population of unlensed source galaxies. Our BFD implementation measures ~10 galaxies per second per core on current hardware, a speed that will be largely independent of the number of images taken of each target. Initial tests of this code on ~400 million simulated lensed galaxy images recover the simulated shear to a fractional accuracy of m=(2.2+-0.6)x10^{-3}, substantially more accurate than has been demonstrated previously for any generally applicable method. The method is readily extended to use multiple exposures in multiple filters. Deep sky exposures generate a sufficiently accurate approximation to the noiseless, unlensed galaxy population distribution assumed as input to BFD. We describe the remaining challenges for applying the BFD method to current and future surveys, as well as potential further extensions, such as simultaneous measurement of magnification and shear; multi-band observations; and joint inference of photometric redshifts and lensing tomography.
G. Bernstein, R. Armstrong, C. Krawiec, et. al.
Tue, 25 Aug 15
21/69
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