Precision simulation of ground-based lensing data using observations from space

Creators: Mandelbaum, Rachel; Hirata, Christopher M.; Leauthaud, Alexie; Massey, Richard J.; Rhodes, Jason

Abstract

Current and upcoming wide-field, ground-based, broad-band imaging surveys promise to address a wide range of outstanding problems in galaxy formation and cosmology. Several such uses of ground-based data, especially weak gravitational lensing, require highly precise measurements of galaxy image statistics with careful correction for the effects of the point spread function (PSF). In this paper, we introduce the shera (SHEar Reconvolution Analysis) software to simulate ground-based imaging data with realistic galaxy morphologies and observing conditions, starting from space-based data (from the Cosmological Evolution Survey, COSMOS) and accounting for the effects of the space-based PSF. This code simulates ground-based data, optionally with a weak lensing shear applied, in a model-independent way using a general Fourier space formalism. The utility of this pipeline is that it allows for a precise, realistic assessment of systematic errors due to the method of data processing, for example in extracting weak lensing galaxy shape measurements or galaxy radial profiles, given user-supplied observational conditions and real galaxy morphologies. Moreover, the simulations allow for the empirical test of error estimates and determination of parameter degeneracies, via generation of many noise maps. The public release of this software, along with a large sample of cleaned COSMOS galaxy images (corrected for charge transfer inefficiency), should enable upcoming ground-based imaging surveys to achieve their potential in the areas of precision weak lensing analysis, galaxy profile measurement and other applications involving detailed image analysis.

Additional Information

© 2011 The Authors. Monthly Notices of the Royal Astronomical Society © 2011 RAS. Accepted 2011 November 3. Received 2011 October 10; in original form 2011 July 23. Article first published online: 13 Dec 2011. We thank the referee for many constructive comments about the organization and content of this paper. The authors would also like to thank Jim Gunn, Robert Lupton, Dustin Lang, David Hogg, Michael Blanton, Barney Rowe, Peter Capak, Chiaki Hikage, Uros Seljak and Gary Bernstein for useful conversations about this project, and Eric Huff both for discussing it and giving the software a name. CMH is supported by the US National Science Foundation (AST-0807337), the US Department of Energy (DE-FG03- 02-ER40701), the Alfred P. Sloan Foundation, and the David and Lucile Packard Foundation. AL acknowledges support from the Chamberlain Fellowship at LBNL and from the Berkeley Center for Cosmological Physics. RJM is supported by STFC Advanced Fellowship #PP/E006450/1 and ERC grant MIRG-CT-208994. This work was done in part at JPL, run under a contract for NASA by Caltech. The HST COSMOS Treasury programme was supported through NASA grant HST-GO-09822. We wish to thank Tony Roman, Denise Taylor and David Soderblom for their assistance in planning and scheduling of the extensive COSMOS observations. We gratefully acknowledge the contributions of the entire COSMOS collaboration consisting of more than 70 scientists. More information on the COSMOS survey is available at http://cosmos.astro.caltech.edu/. It is a pleasure to acknowledge the excellent services provided by the NASA IPAC/IRSA staff (Justin Howell, Anastasia Laity, Anastasia Alexov, Bruce Berriman and John Good) in providing online archive and server capabilities for the COSMOS data sets.

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