Self Calibration of Gravitational Shear-galaxy Intrinsic Ellipticity Correlation in Weak Lensing Surveys
نویسنده
چکیده
The existence of non-random galaxy intrinsic ellipticity severely challenges precision cosmic shear measurement. We propose to self calibrate the induced gravitational shear-galaxy intrinsic ellipticity contamination (the GI correlation, Hirata & Seljak 2004) using extra information encoded in the same weak lensing survey. Besides the galaxy ellipticity-galaxy ellipticity correlation, the same lensing survey also measures the galaxy ellipticity-galaxy density and galaxy density-galaxy density correlations. A subset of these extra correlations can be converted into a measure of the GI correlation, in a rather model independent and predictable way. This self calibration technique is applicable to weak lensing surveys with photometric redshift information, with virtually no loss in cosmological information. It can suppress the GI contamination by a factor of 10, or reduce it to below the statistical limit of the cosmic shear measurement. It also sheds light on correcting the intrinsic ellipticity-intrinsic ellipticity contamination. Subject headings: cosmology: gravitational lensing–theory
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