image processing for weak lensing
DESCRIPTION
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. - PowerPoint PPT PresentationTRANSCRIPT
Image Processing for Weak Lensing
Wentao LuoSHAO
May 14, 2014 NAOC
Contents
• Weak Gravitational Lensing
• Accurate image processing—PSF correction
• Reconstruct the density field using weak lensing.
2 2 2 22 2
2 2 2 2 21 1 2
2 2(1 ) (1 )
{ ( )[ cos ( ) ]}k
ds c dt ac c
dw f w d d
2
2dl
c
Hilbert et al 2009
3
2observer
sourcet dl
c Time delay:
Deflection angle:
Narayan & Bartelmann
1997
2 ( )ij ij
i j
A
1 2
2 1
1
1A
1 2i
Jacobian
Narayan & Bartelmann 1997
int 2e e R
int 2e e R
2e R
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
Input Input imageimage
PSF PSF imageimage
BJ02BJ02 Image Image convolved convolved
with with KernelKernel
re-re-GaussianizGaussianized imageed imageHS03HS03
Bernstein & Jarvis 2002; Hirata & Seljak 2003
RR
ee++,e,exx
OutOutputput
Testing
SHERA Mandelbaum et al 2011
Deconvole HST psf, re-convolve SDSS PSF
SDSS pixelsize+SDSS noise
Reality is cruel!!
Jun Zhang Methods
GREAT3 Results
---------------------------------------------------------------
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