We use South Pole Telescope data from 2008 and 2009 to detect the non-Gaussian signature in the cosmic microwave background ( CMB ) produced by gravitational lensing and to measure the power spectrum of the projected gravitational potential .
We constrain the ratio of the measured amplitude of the lensing signal to that expected in a fiducial \Lambda CDM cosmological model to be 0.86 \pm 0.16 , with no lensing disfavored at 6.3 \sigma .
Marginalizing over \Lambda CDM cosmological models allowed by the Wilkinson Microwave Anisotropy Probe ( WMAP7 ) results in a measurement of A _ { lens } = 0.90 \pm 0.19 , indicating that the amplitude of matter fluctuations over the redshift range 0.5 \lesssim z \lesssim 5 probed by CMB lensing is in good agreement with predictions .
We present the results of several consistency checks .
These include a clear detection of the lensing signature in CMB maps filtered to have no overlap in Fourier space , as well as a “ curl ” diagnostic that is consistent with the signal expected for \Lambda CDM .
We perform a detailed study of bias in the measurement due to noise , foregrounds , and other effects and determine that these contributions are relatively small compared to the statistical uncertainty in the measurement .
We combine this lensing measurement with results from WMAP7 to improve constraints on cosmological parameters when compared to those from WMAP7 alone : we find a factor of 3.9 improvement in the measurement of the spatial curvature of the Universe , \Omega _ { k } = -0.0014 \pm 0.0172 ; a 10 % improvement in the amplitude of matter fluctuations within \Lambda CDM , \sigma _ { 8 } = 0.810 \pm 0.026 ; and a 5 % improvement in the dark energy equation of state , w = -1.04 \pm 0.40 .
When compared with the measurement of w provided by the combination of WMAP7 and external constraints on the Hubble parameter , the addition of the lensing data improve the measurement of w by 15 % to give w = -1.087 \pm 0.096 .