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Published July 1, 2010 | Published
Journal Article Open

Results of the GREAT08 Challenge: an image analysis competition for cosmological lensing

Abstract

We present the results of the Gravitational LEnsing Accuracy Testing 2008 (GREAT08) Challenge, a blind analysis challenge to infer weak gravitational lensing shear distortions from images. The primary goal was to stimulate new ideas by presenting the problem to researchers outside the shear measurement community. Six GREAT08 Team methods were presented at the launch of the Challenge and five additional groups submitted results during the 6-month competition. Participants analyzed 30 million simulated galaxies with a range in signal-to-noise ratio, point spread function ellipticity, galaxy size and galaxy type. The large quantity of simulations allowed shear measurement methods to be assessed at a level of accuracy suitable for currently planned future cosmic shear observations for the first time. Different methods perform well in different parts of simulation parameter space and come close to the target level of accuracy in several of these. A number of fresh ideas have emerged as a result of the Challenge including a re-examination of the process of combining information from different galaxies, which reduces the dependence on realistic galaxy modelling. The image simulations will become increasingly sophisticated in future GREAT Challenges, meanwhile the GREAT08 simulations remain as a benchmark for additional developments in shear measurement algorithms.

Additional Information

© 2010 The Authors. Journal compilation © 2010 RAS. Accepted 2010 February 26. Received 2010 January 21; in original form 2009 August 7. We thank the PASCAL Network for support. We thank the GREAT08 Team and participants at the GREAT08 Mid-Challenge Workshop and GREAT08 Final Workshop including Hakon Dahle, Domenico Marinucci and Uros Seljak. We thank the organizers of Cosmostats09 for hosting the GREAT08 Challenge Final Workshop within Cosmostats09 in Ascona. We thank the Aspen Center for Physics where part of this work was carried out.We are grateful to Jeremy Yates for help with setting up the GREAT08 server. SLB thanks the Royal Society for support in the form of a University Research Fellowship. TDK is supported by STFC Rolling grant RA0888. JR is supported in part by the Jet Propulsion Laboratory, which is run by Caltech under a contract from NASA. MS was supported in part by the programme 11288 provided by NASA through a grant from the STScI, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555.

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