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G. M. Bernstein, R. M. Jarvis, B. Jain (University of Pennsylvania)
We measure seeing-corrected ellipticities for 2\times106 galaxies with magnitude R\le23 in 12 widely separated fields totalling 75~deg2 of sky. At angular scales \gtrsim30\arcmin, ellipticity correlations are detected at high significance and exhibit nearly the pure ``E-mode'' behavior expected of weak gravitational lensing. Even when smoothed to the full field size of 2\fdg5, which is \approx25h-1~Mpc at the lens distances, an rms shear variance of \langle \gamma2 \rangle1/2=0.0012±.0003 is detected. The >30\arcmin data constrain the power spectrum of matter fluctuations on comoving scales of \approx10h-1~Mpc to have \sigma8 (\Omegam/0.3)0.57 = 0.71+0.12-0.16 (95% CL, \LambdaCDM, \Gamma=0.21), where the systematic error includes statistical and calibration uncertainties, cosmic variance, and a conservative estimate of systematic contamination based upon the detected B-mode signal. This normalization of the power spectrum is lower than previous weak-lensing results but consistent with all but one of them, is at the lower end of the \sigma8 range from various analyses of galaxy cluster abundances, and agrees with recent determinations from CMB and galaxy clustering.
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Bulletin of the American Astronomical Society, 34, #4
© 2002. The American Astronomical Soceity.