A fast empirical method for galaxy shape measurements in weak lensing surveys

Details A fast empirical method for galaxy shape measurements in weak lensing surveys A fast empirical method for galaxy shape measurements in weak lensing surveys

2012-03-20

arxiv.org/abs/1203.4429v1

Astronomy and Astrophysics

Astrophysics

Cosmology and Extragalactic Astrophysics

8 pages, 6 figures, submitted to A&A. Associated code available at http://lastro.epfl.ch/megalut

Scientific paper

We describe a simple and fast method to correct ellipticity measurements of galaxies from the distortion by the instrumental and atmospheric point spread function (PSF), in view of weak lensing shear measurements. The method performs a classification of galaxies and associated PSFs according to measured shape parameters, and corrects the measured galaxy ellipticites by querying a large lookup table (LUT), built by supervised learning. We have applied this new method to the GREAT10 image analysis challenge, and present in this paper a refined solution that obtains the highly competitive quality factor of Q = 142, without any power spectrum denoising or training. Of particular interest is the efficiency of the method, with a processing time below 3 ms per galaxy on an ordinary CPU.

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