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Image Processing for Weak Lensing

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.

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Image Processing for Weak Lensing

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

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

  3. Time delay: Deflection angle: Hilbert et al 2009

  4. Narayan & Bartelmann 1997

  5. Jacobian

  6. Narayan & Bartelmann 1997

  7. Point Spread Function

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

  9. 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

  10. Re-Gaussianization

  11. Rounding Kernel

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

  13. Testing

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

  15. Jun Zhang Methods

  16. GREAT3 Results

  17. ------------------------------------------------------------------------------------------------------------------------------

  18. 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

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