Journal
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
Volume -, Issue 1, Pages -Publisher
IOP PUBLISHING LTD
DOI: 10.1088/1475-7516/2015/01/024
Keywords
weak gravitational lensing; gravitational lensing
Funding
- national science foundation of China [11273018, 11133001]
- national basic research program of China [2013CB834900, 2015CB857001]
- national Thousand Talents Program for distinguished young scholars from the Office of Science and Technology in Shanghai Municipal Government [11DZ2260700]
- High Energy Physics Center of Peking University
- TCC Fellowship of Texas Cosmology Center of the University of Texas at Austin
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For cosmic shear to become an accurate cosmological probe, systematic errors in the shear measurement method must be unambiguously identified and corrected for Previous work of this series has demonstrated that cosmic shears can be measured accurately in Fourier space in the presence of background noise and finite pixel size, without assumptions on the morphologies of galaxy and PSF. The remaining major source of error is source Poisson noise, due to the finiteness of source photon number. This problem is particularly important for faint galaxies in space-based weak lensing measurements, and for ground-based images of short exposure times. In this work, we propose a simple and rigorous way of removing the shear bias from the source Poisson noise. Our noise treatment, can be generalized for images made of multiple exposures through Multi Drizzle. This is demonstrated with the SDSS and COSMOS/ACS data. With a large ensemble of mock galaxy images of unrestricted morphologies, we show that our shear measurement method can achieve sub-percent level accuracy even for images of signal-to-noise ratio less than 5 in general, making it the most promising technique for cosmic shear measurement in the ongoing and upcoming large scale galaxy surveys.
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