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The stability of the point-spread function of the advanced camera for surveys on the Hubble Space Telescope and implications for weak gravitational lensing

Rhodes, Jason D.; Massey, Richard J.; Albert, Justin; Collins, Nicholas; Ellis, Richard S.; Heymans, Catherine; Gardner, Jonathan P.; Kneib, Jean-Paul; Koekemoer, Anton; Leauthaud, Alexie; Mellier, Yannick; Refregier, Alexander; Taylor, James E.; Van Waerbeke, Ludovic

The stability of the point-spread function of the advanced camera for surveys on the Hubble Space Telescope and implications for weak gravitational lensing Thumbnail


Authors

Jason D. Rhodes

Justin Albert

Nicholas Collins

Richard S. Ellis

Catherine Heymans

Jonathan P. Gardner

Jean-Paul Kneib

Anton Koekemoer

Alexie Leauthaud

Yannick Mellier

Alexander Refregier

James E. Taylor

Ludovic Van Waerbeke



Abstract

We examine the spatial and temporal stability of the Hubble Space Telescope's Advanced Camera for Surveys (ACS) Wide Field Camera (WFC) point-spread function (PSF) using the 2 deg2 COSMOS survey. This is important for studies of weak gravitational lensing, where the ability to deconvolve the PSF from galaxy shapes is of paramount importance. We show that stochastic aliasing of the PSF necessarily occurs during "drizzling." This aliasing is maximal if the output-pixel scale is equal to the input-pixel scale. This source of PSF variation can be significantly reduced by choosing a Gaussian drizzle kernel with a size of 0.8 input pixels and by reducing the output-pixel scale. We show that the PSF is temporally unstable, resulting in an overall slow periodic focus change in the COSMOS images. Using a modified version of the Tiny Tim PSF modeling software, we create grids of undistorted stars over a range of telescope focus values. We then use the approximately 10 well-measured stars in each COSMOS field to pick the best-fit focus value for each field. The Tiny Tim model stars can then be used to perform PSF corrections for weak lensing. We derive a parametric correction for the effect of charge transfer efficiency (CTE) degradation on the shapes of objects in the COSMOS field as a function of observation date, position within the ACS WFC field, and object flux. Finally, we discuss future plans to improve the CTE correction.

Citation

Rhodes, J. D., Massey, R. J., Albert, J., Collins, N., Ellis, R. S., Heymans, C., …Van Waerbeke, L. (2007). The stability of the point-spread function of the advanced camera for surveys on the Hubble Space Telescope and implications for weak gravitational lensing. Astrophysical Journal Supplement, 172(1), 203-218. https://doi.org/10.1086/516592

Journal Article Type Article
Publication Date Sep 1, 2007
Deposit Date Mar 21, 2013
Publicly Available Date Mar 29, 2024
Journal Astrophysical Journal Supplement
Print ISSN 0067-0049
Electronic ISSN 1538-4365
Publisher American Astronomical Society
Peer Reviewed Peer Reviewed
Volume 172
Issue 1
Pages 203-218
DOI https://doi.org/10.1086/516592

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Copyright Statement
© 2007. The American Astronomical Society. All rights reserved. Printed in U.S.A.





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