Shapelets analysis of weak lensing surveys Joel Bergé (CEA Saclay) with Richard Massey (Caltech)...
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Transcript of Shapelets analysis of weak lensing surveys Joel Bergé (CEA Saclay) with Richard Massey (Caltech)...
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 (CEA Saclay)with
Richard Massey (Caltech)
Alexandre Refregier (CEA Saclay)
Joel Bergé - 03-22-2006 - Rencontres de Moriond
Observation of cosmic shearObservation of cosmic shear
Distant galaxiesLensed galaxies Dark matter distributionand map of shear
The shear measurement challenge
Shear measurement error is one predominant systematic
Intrinsic ellipticities
PSF (response of the telescope)
Pixelization
Noise
8
-8
-6
-4
-2
6
4
2
0
ShapeletsShapelets
n
m
0 1 2 3 4 5 6 7 8
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
nmax
Shapelets pipelineShapelets pipelineLeast-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
PSF modelPSF modelStars selected then decomposed into shapelets, the order of decomposition depending on data
nmax=28
nmax=10Subaru
CFHT
FWHM ~0.5 arcsec
FWHM ~0.7 arcsec
Wing
PSF interpolationPSF interpolation
Measured PSF
Residuals
Model
CFHT/Megacam D1 field
CFHT/Megacam D1 field
Scale : 8%
Model created by interpolating shapelet
coefficients of stars with a polynomial
Blind test with simulations : STEP (Shear TEsting Programme)
Blind test with simulations : STEP (Shear TEsting Programme)
Heymans et al, 2006Massey et al, 2006, in preparation
Simulation Real image
Aims at comparing and improving existing cosmic shear measurement techniques.Realistic cosmic shear simulations, of ground based weak lensing surveys.
Shapelets STEP resultsShapelets STEP results
1 PSF, 64 input shears
Input shear
Mea
sure
d sh
ear
CFHT/MegacamCFHT/MegacamJ. Bergé, A. Refregier et al
E mode B mode
Mass inversion using wavelets (Starck, Pires & Refregier 2005), cf S. Pires’ poster
SubaruSubaru
QuickTime™ et undécompresseur TIFF (LZW)
sont requis pour visionner cette image.
-3.0
-3.5
-4.0
-4.5
-5.0 37 35.536.036.5
KSB (S. Miyazaki)
S. Miyazaki, R. Massey, J. Bergé, A. Refregier, T. Hamana, R. Ellis
Shapelets (Megacam)
C2
C3
ConclusionsConclusionsShapelets 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