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Shapelets analysis of weak lensing surveys

Shapelets analysis of weak lensing surveys. Joel Bergé (CEA Saclay) with Richard Massey (Caltech) Alexandre Refregier (CEA Saclay). Joel Bergé - 03-22-2006 - Rencontres de Moriond. Observation of cosmic shear. The shear measurement challenge. Intrinsic ellipticities

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Shapelets analysis of weak lensing surveys

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  1. Shapelets analysis of weak lensing surveys Joel Bergé (CEA Saclay) with Richard Massey (Caltech) Alexandre Refregier (CEA Saclay) Joel Bergé - 03-22-2006 - Rencontres de Moriond

  2. Observation of cosmic shear The shear measurement challenge Intrinsic ellipticities PSF (response of the telescope) Pixelization Noise Shear measurement error is one predominant systematic We need a precise and accurate shape measurement method Shapelets Dark matter distribution Distant galaxies Lensed galaxies and map of shear

  3. 8 6 4 2 0 -2 -4 -6 -8 0 1 2 3 4 5 6 7 8 Shapelets nmax Refregier 2003, Refregier & Bacon 2003, Massey & Refregier 2005 n,m Complete orthogonal basis functions Capture all shape information of an object Simple and analytic form for convolution and shear Adapted to cosmic shear m n

  4. Shapelets pipeline Least-square fitting of an analytical model (pixelized and convolved with the PSF) to observed data. Shapelet model of the observed galaxy Residuals Galaxy to be fitted Convolution in shapelets space Shear estimator Shapelet model of the PSF Shapelet model of the galaxy, deconvolved from the PSF

  5. PSF model • Stars selected then decomposed into shapelets, the order of decomposition depending on data FWHM ~0.5 arcsec Subaru nmax=10 FWHM ~0.7 arcsec Wing nmax=28 CFHT

  6. CFHT/Megacam D1 field Scale : 8% PSF interpolation Model created by interpolating shapelet coefficients of stars with a polynomial Measured PSF Model Residuals

  7. Blind test with simulations : STEP (Shear TEsting Programme) Heymans et al, 2006 Massey et al, 2006, in preparation Aims at comparing and improving existing cosmic shear measurement techniques. Realistic cosmic shear simulations, of ground based weak lensing surveys. Simulation Real image

  8. Measured shear Input shear 1 PSF, 64 input shears Shapelets STEP results

  9. CFHT/Megacam J. Bergé, A. Refregier et al Mass inversion using wavelets (Starck, Pires & Refregier 2005), cf S. Pires’ poster E mode B mode

  10. C2 C3 Subaru S. Miyazaki, R. Massey, J. Bergé, A. Refregier, T. Hamana, R. Ellis KSB (S. Miyazaki) -3.0 Shapelets (Megacam) -3.5 -4.0 -4.5 -5.0 37 36.5 36.0 35.5

  11. Conclusions Shapelets are now reliable for weak lensing high precision measurement Already used (preliminary results) on Subaru and CFHTLS Deep data Will be used to analyse current Subaru survey and CFHTLS Wide data Potential comparison Subaru-CFHT-COSMOS Software package and documentation http://www.astro.caltech.edu/~rjm/shapelets/ http://www.astro.caltech.edu/~jberge/shapelets/

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