Measurement of the gravitational potential evolution from the cross-correlation between WMAP and the APM Galaxy survey

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  • 13 November 2003
Abstract
Models with late time cosmic acceleration, such as the Lambda-dominated CDM model, predict a freeze out for the growth of linear gravitational potential at moderate redshift z<1, which can be observed as temperature anisotropies in the CMB: the so called integrated Sachs-Wolfe (ISW) effect. We present a direct measurement of the ISW effect based on the angular cross-correlation function, w_{TG}, of CMB temperature anisotropies and dark-matter fluctuations traced by galaxies. We cross-correlate the first-year WMAP data in combination with the APM Galaxy survey. On the largest scales, theta = 4-10 deg, we detect a non-vanishing cross-correlation at 98.8 % significance level, with a 1-sigma error of w_{TG} = 0.35 +/- 0.14 microK, which favors large values of Omega_Lambda \simeq 0.8 for flat FRW models. On smaller scales, theta < 1 deg, one expects a comparable ISW contribution. Instead we find a negative correlation, w_{TG} = -0.41 +/- 0.14 +/- 0.16 microK, what can be interpreted as a signal from the thermal Sunyaev-Zeldovich (SZ) effect.

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