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Pixelation Effects in Weak LensingWeak 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, and 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 ~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.
Document ID
20080045906
Acquisition Source
Jet Propulsion Laboratory
Document Type
Reprint (Version printed in journal)
External Source(s)
Authors
High, F. William
(Harvard Univ. Cambridge, MA, United States)
Rhodes, Jason
(Jet Propulsion Lab., California Inst. of Tech. Pasadena, CA, United States)
Massey, Richard
(California Inst. of Tech. Pasadena, CA, United States)
Ellis, Richard
(California Inst. of Tech. Pasadena, CA, United States)
Date Acquired
August 24, 2013
Publication Date
December 3, 2007
Publication Information
Publication: Publications of the Astronomical Society of the Pacific
Publisher: Astronomical Society of the Pacific
Volume: 119
Subject Category
Astronomy
Funding Number(s)
CONTRACT_GRANT: DE-FG02-04ER41316
Distribution Limits
Public
Copyright
Other
Keywords
gravitational lensing
dark energy
pixel scale
dark matter

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