A MEASUREMENT OF GRAVITATIONAL LENSING OF THE MICROWAVE BACKGROUND USING SOUTH POLE TELESCOPE DATA

Abstract

We use South Pole Telescope data from 2008 and 2009 to detect the\nnon-Gaussian signature in the cosmic microwave background (CMB) produced by\ngravitational lensing and to measure the power spectrum of the projected\ngravitational potential. We constrain the ratio of the measured amplitude of\nthe lensing signal to that expected in a fiducial LCDM cosmological model to be\n0.86 +/- 0.16, with no lensing disfavored at 6.3 sigma. Marginalizing over LCDM\ncosmological models allowed by the WMAP7 results in a measurement of\nA_lens=0.90+/-0.19, indicating that the amplitude of matter fluctuations over\nthe redshift range 0.5 <~ z <~ 5 probed by CMB lensing is in good agreement\nwith predictions. We present the results of several consistency checks. These\ninclude a clear detection of the lensing signature in CMB maps filtered to have\nno overlap in Fourier space, as well as a "curl" diagnostic that is consistent\nwith the signal expected for LCDM. We perform a detailed study of bias in the\nmeasurement due to noise, foregrounds, and other effects and determine that\nthese contributions are relatively small compared to the statistical\nuncertainty in the measurement. We combine this lensing measurement with\nresults from WMAP7 to improve constraints on cosmological parameters when\ncompared to those from WMAP7 alone: we find a factor of 3.9 improvement in the\nmeasurement of the spatial curvature of the Universe, Omega_k=-0.0014+/-0.0172;\na 10% improvement in the amplitude of matter fluctuations within LCDM,\nsigma_8=0.810+/ 0.026; and a 5% improvement in the dark energy equation of\nstate, w=-1.04+/-0.40. When compared with the measurement of w provided by the\ncombination of WMAP7 and external constraints on the Hubble parameter, the\naddition of the lensing data improve the measurement of w by 15% to give\nw=-1.087+/-0.096.\n