1. Shapelets analysis of weak lensing surveys Joel Bergé (CEA Saclay) with Richard Massey (Caltech) Alexandre Refregier (CEA Saclay) 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 Distant galaxiesLensed galaxies Dark matter distribution and map of shear The shear measurement challenge Shear measurement error is one predominant systematic Intrinsic ellipticities PSF (response of the telescope) Pixelization Noise

3. 8 -8 -6 -4 -2 6 4 2 0 Shapelets n m 012345678 Complete orthogonal basis functions Capture all shape information of an object Simple and analytic form for convolution and shear Adapted to cosmic shear  n,m Refregier 2003, Refregier & Bacon 2003, Massey & Refregier 2005 n max

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

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

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

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

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

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

10. Subaru -3.0 -3.5 -4.0 -4.5 -5.0 3735.536.036.5 KSB (S. Miyazaki) S. Miyazaki, R. Massey, J. Bergé, A. Refregier, T. Hamana, R. Ellis Shapelets (Megacam) C2 C3

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 http://www.astro.caltech.edu/~rjm/shapelets/ http://www.astro.caltech.edu/~jberge/shapelets/ Software package and documentation