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.

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

6. Narayan & Bartelmann 1997

7. Jacobian

8. Narayan & Bartelmann 1997

10. Point Spread Function

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

12. 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

13. Re-Gaussianization

14. Rounding Kernel

15. 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

16. Testing

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

20. Jun Zhang Methods

21. GREAT3 Results

22. ---------------------------------------------------------------

27. 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