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Pixelation effects in weak lensing

High, F. William and Rhodes, Jason and Massey, Richard and Ellis, Richard (2007) Pixelation effects in weak lensing. Publications of the Astronomical Society of the Pacific, 119 (861). pp. 1295-1307. ISSN 0004-6280. doi:10.1086/523112.

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Weak gravitational lensing can be used to investigate both dark matter and dark energy but requires accurate measurements of the shapes of faint, distant galaxies. Such measurements are hindered by the finite resolution and pixel scale of digital cameras. We investigate the optimum choice of pixel scale for a space-based mission, using the engineering model and survey strategy of the proposed Supernova Acceleration Probe as a baseline. We do this by simulating realistic astronomical images containing a known input shear signal and then attempting to recover the signal using the Rhodes, Refregier, & Groth algorithm. We find that the quality of shear measurement is always improved by smaller pixels. However, in practice, telescopes are usually limited to a finite number of pixels and operational life span, so the total area of a survey increases with pixel size. We therefore fix the survey lifetime and the number of pixels in the focal plane while varying the pixel scale, thereby effectively varying the survey size. In a pure trade-off for image resolution versus survey area, we find that measurements of the matter power spectrum would have minimum statistical error with a pixel scale of 0.09 '' for a 0.14 '' FWHM point-spread function (PSF). The pixel scale could be increased to similar to 0.16 '' if images dithered by exactly half-pixel offsets were always available. Some of our results do depend on our adopted shape measurement method and should be regarded as an upper limit: future pipelines may require smaller pixels to overcome systematic floors not yet accessible, and, in certain circumstances, measuring the shape of the PSF might be more difficult than those of galaxies. However, the relative trends in our analysis are robust, especially those of the surface density of resolved galaxies. Our approach thus provides a snapshot of potential in available technology, and a practical counterpart to analytic studies of pixelation, which necessarily assume an idealized shape measurement method.

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Ellis, Richard0000-0001-7782-7071
Additional Information:© 2007 The Astronomical Society of the Pacific. Received 2007 March 17; accepted 2007 September 6; published 2007 December 3. We are grateful to Steve Kent for providing ray‐tracing software configured for the SNAP design. We also thank Alexandre Refregier, David Johnston, Matt Ferry, Gary Bernstein, Mike Jarvis, Molly Peeples, Chris Stubbs, and Adam Amara for useful discussions. The Parallel Distributed Systems Facility, a Linux cluster run by the Department of Energy’s National Energy Research Scientific Computing Center, made our large‐scale simulations and analysis possible: we particularly thank Iwona Sakrejda for consultation. The research described in this paper was carried out in part at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration; as well as at the California Institute of Technology main campus. This research was supported in part by a 2004 Caltech Summer Undergraduate Research Fellowship and Department of Energy grant DE‐FG02‐04ER41316.
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Caltech Summer Undergraduate Research Fellowship (SURF)UNSPECIFIED
Department of Energy (DOE)DE-FG02-04ER41316
Issue or Number:861
Record Number:CaltechAUTHORS:HIGpasp07
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:13239
Deposited By: Tony Diaz
Deposited On:04 Feb 2009 21:36
Last Modified:08 Nov 2021 22:36

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