Reconstruction of gravitational lensing using WMAP 7-year data

Gravitational lensing by large scale structure introduces non-Gaussianity into the cosmic microwave background and imprints a new observable, which can be used as a cosmological probe. We apply a four-point estimator to the Wilkinson Microwave Anisotropy Probe (WMAP) 7-year coadded temperature maps alone to reconstruct the gravitational lensing signal. The Gaussian bias is simulated and subtracted, and the higher-order bias is investigated. We measure a gravitational lensing signal with a statistical amplitude of C=1.27±0.98 using all the correlations of the W- and V-band differencing assemblies . We therefore conclude that WMAP 7-year data alone cannot detect lensing.