Cosmic Shear Measurement In The6^th Release Data Of CFHTLS Deep Survey

Cosmic shear is the weak lensing effect caused by the large-scalestructure of the Universe. Lights emitted by distant galaxies aredeflected by the foreground gravitational field, thus the apparentellipticities of galaxies are distorted. The distribution of dark matter,properties of dark energy and the large-scale structure of the Universecan be studied by means of the statistical properties of cosmic shear.In this thesis work, the weak gravitational lensing is analyzed byusing the sixth year Canada-France-Hawaii Telescope Legacy Survey(CFHTLS) Deep data release. The25%best seeing r-band images of theD1, D2, D3and D4fields are used for analysis. The anisotropic pointspread functions (PSF) are corrected by using the Kaiser, Squires andBroadhurst (KSB) method. Three kinds of two-point correlations ofcosmic shear are provided, and the lensing (E-mode) and non-lensing(B-mode) signal are decomposed in the thesis.From the weighted average results of three two-point correlationsfrom D1, D2, D3and D4fields, we found the E-/B-mode are clearlydecomposed. The B-mode are nearly vanished within the statistic error.That means, the PSF anisotropic correct in the thesis were wellcontrolled, and the systematic uncertainties are acceptable. Thus, theE-mode (the lensing signal) from the thesis work is credible.Furthermore, the E-/B-mode signal of three kinds of two-pointcorrelations from D1, D2, D3and D4four individual fields are comparedfor crosscheck. The E-/B-mode signal are consistent within their statisticerrors. The shear and star ellipticity correlation, ξsys, is also calculated inthe thesis. It is much smaller than the shear-shear correlation(ξE), whichproves the PSF anisotropic correction is well done.The photometric redshift of the galaxies in our shear catalog canbe obtained from the released photometric redshift catalog of CFHTLS fourth release. The average redshift of our shear sample is1.24. Theredshift information will be useful for the constraints of cosmologicalparameters in the next step work.