Image Processing for Weak Lensing Wentao Luo SHAO May 14, 2014 NAOC

Contents Weak Gravitational Lensing Accurate image processing—PSF correction Reconstruct the density field using weak lensing.

Time delay: Deflection angle: Hilbert et al 2009

Narayan & Bartelmann 1997

Jacobian

Narayan & Bartelmann 1997

Point Spread Function

<e_psf>~0.45 for SDSS while shear signal ~0.01

Methods Traditional methods 2, Re-Gaussianization (Hirata & Seljak 2003) 3, Rounding Kernel (Bernstein & jarvis 2002) 4, Shapelets (Refregier 2000) Jun Zhang 2008; Jun Zhang 2010; Jun Zhang, WTL & Sebastien. Foucaud 2014

Re-Gaussianization

Rounding Kernel

The Structure of Our Pipeline re-Gaussianized image Input image R HS03 Out put PSF image BJ02 Image convolved with Kernel e+,ex Bernstein & Jarvis 2002; Hirata & Seljak 2003

Testing

SHERA Mandelbaum et al 2011 Reality is cruel!! Deconvole HST psf, re-convolve SDSS PSF SDSS pixelsize+SDSS noise Reality is cruel!!

Jun Zhang Methods

GREAT3 Results

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Conclusion Accurate image processing is the first step for weak lensing study Simulations to test your pipeline We can use real data to do the comparison among various methods Potential systematic from image itself Moving to real data