Astronomy and Astrophysics – Astrophysics – Cosmology and Extragalactic Astrophysics
Scientific paper
2012-02-23
Astronomy and Astrophysics
Astrophysics
Cosmology and Extragalactic Astrophysics
50 pages, 47 figures, submitted to MNRAS
Scientific paper
In this paper we present results from the weak lensing shape measurement GRavitational lEnsing Accuracy Testing 2010 (GREAT10) Galaxy Challenge. This marks an order of magnitude step change in the level of scrutiny employed in weak lensing shape measurement analysis. We provide descriptions of each method tested and include 10 evaluation metrics over 24 simulation branches. GREAT10 was the first shape measurement challenge to include variable fields; both the shear field and the Point Spread Function (PSF) vary across the images in a realistic manner. The variable fields enable a variety of metrics that are inaccessible to constant shear simulations including a direct measure of the impact of shape measurement inaccuracies, and the impact of PSF size and ellipticity, on the shear power spectrum. To assess the impact of shape measurement bias for cosmic shear we present a general pseudo-Cl formalism, that propagates spatially varying systematics in cosmic shear through to power spectrum estimates. We also show how one-point estimators of bias can be extracted from variable shear simulations. The GREAT10 Galaxy Challenge received 95 submissions and saw a factor of 3 improvement in the accuracy achieved by shape measurement methods. The best methods achieve sub-percent average biases. We find a strong dependence in accuracy as a function of signal-to-noise, and indications of a weak dependence on galaxy type and size. Some requirements for the most ambitious cosmic shear experiments are met above a signal-to-noise ratio of 20. These results have the caveat that the simulated PSF was a ground-based PSF. Our results are a snapshot of the accuracy of current shape measurement methods and are a benchmark upon which improvement can continue. This provides a foundation for a better understanding of the strengths and limitations of shape measurement methods.
Balan Sreekumar T.
Bridle Sarah
Cantale N.
Courbin Fred
Gentile Marc
No associations
LandOfFree
Image Analysis for Cosmology: Results from the GREAT10 Galaxy Challenge does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.
If you have personal experience with Image Analysis for Cosmology: Results from the GREAT10 Galaxy Challenge, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Image Analysis for Cosmology: Results from the GREAT10 Galaxy Challenge will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-660899