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Cosmic shear requirements on the wavelength dependence of telescope point spread functions

Cypriano, E. S. and Amara, A. and Voigt, L. M. and Bridle, S. L. and Abdalla, F. B. and Réfrégier, A. and Seiffert, M. and Rhodes, J. (2010) Cosmic shear requirements on the wavelength dependence of telescope point spread functions. Monthly Notices of the Royal Astronomical Society, 405 (1). pp. 494-502. ISSN 0035-8711.

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Cosmic shear requires high precision measurement of galaxy shapes in the presence of the observational point spread function (PSF) that smears out the image. The PSF must therefore be known for each galaxy to a high accuracy. However, for several reasons, the PSF is usually wavelength dependent; therefore, the differences between the spectral energy distribution of the observed objects introduce further complexity. In this paper, we investigate the effect of the wavelength dependence of the PSF, focusing on instruments in which the PSF size is dominated by the diffraction limit of the telescope and which use broad-band filters for shape measurement. We first calculate biases on cosmological parameter estimation from cosmic shear when the stellar PSF is used uncorrected. Using realistic galaxy and star spectral energy distributions and populations and a simple three-component circular PSF, we find that the colour dependence must be taken into account for the next generation of telescopes.We then consider two different methods for removing the effect: (i) the use of stars of the same colour as the galaxies and (ii) estimation of the galaxy spectral energy distribution using multiple colours and using a telescope model for the PSF. We find that both of these methods correct the effect to levels below the tolerances required for per cent level measurements of dark energy parameters. Comparison of the two methods favours the template-fitting method because its efficiency is less dependent on galaxy redshift than the broad-band colour method and takes full advantage of deeper photometry.

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Additional Information:© 2010 The Authors. Journal compilation © 2010 RAS. Accepted 2010 February 1. Received 2010 January 29; in original form 2010 January 5. We are grateful to Peter Capak for providing the code used to generate the mock photometric catalogue. We thank Mark Cropper, Jerome Amiaux, Peter Doel, Ofer Lahav, James Kingston, Steve Kent, Michelle Antonik, Stephane Paulin-Henriksson, Gary Bernstein, Tom Kitching, Alexie Leauthaud and Gary Bernstein for helpful conversations. ESC acknowledges support from FAPESP (process number 2009/07154-8). LMV acknowledges support from STFC. SLB and FBA thank the Royal Society for support in the form of a University Research Fellowship. The research described in this paper was performed in part at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration
Funding AgencyGrant Number
Fundacao de Amparo a Pesquisa do Estado de Sao Paulo (Brazil)/FAPESP2009/07154-8
Science and Technology Facilities Council (STFC)UNSPECIFIED
Royal Society University Research FellowshipUNSPECIFIED
Subject Keywords:gravitational lensing; cosmology: observations; large-scale structure of Universe
Issue or Number:1
Record Number:CaltechAUTHORS:20100629-132227094
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:18854
Deposited By: Ruth Sustaita
Deposited On:30 Jun 2010 15:14
Last Modified:03 Oct 2019 01:48

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