A MEASUREMENT OF THE COSMIC MICROWAVE BACKGROUND DAMPING TAIL FROM THE 2500-SQUARE-DEGREE SPT-SZ SURVEY

Abstract

We present a measurement of the cosmic microwave background (CMB) temperature power spectrum using data from the recently completed South Pole Telescope Sunyaev–Zel'dovich (SPT-SZ) survey. This measurement is made from observations of 2540 deg 2 of sky with arcminute resolution at 150 GHz, and improves upon previous measurements using the SPT by tripling the sky area. We report CMB temperature anisotropy power over the multipole range 650 < ℓ < 3000. We fit the SPT bandpowers, combined with the 7 yr Wilkinson Microwave Anisotropy Probe ( WMAP 7) data, with a six-parameter ΛCDM cosmological model and find that the two datasets are consistent and well fit by the model. Adding SPT measurements significantly improves ΛCDM parameter constraints; in particular, the constraint on θ s tightens by a factor of 2.7. The impact of gravitational lensing is detected at 8.1σ, the most significant detection to date. This sensitivity of the SPT+ WMAP 7 data to lensing by large-scale structure at low redshifts allows us to constrain the mean curvature of the observable universe with CMB data alone to be . Using the SPT+ WMAP 7 data, we measure the spectral index of scalar fluctuations to be n s = 0.9623 ± 0.0097 in the ΛCDM model, a 3.9σ preference for a scale-dependent spectrum with n s < 1. The SPT measurement of the CMB damping tail helps break the degeneracy that exists between the tensor-to-scalar ratio r and n s in large-scale CMB measurements, leading to an upper limit of r < 0.18 (95% C.L.) in the ΛCDM+ r model. Adding low-redshift measurements of the Hubble constant ( H 0 ) and the baryon acoustic oscillation (BAO) feature to the SPT+ WMAP 7 data leads to further improvements. The combination of SPT+ WMAP 7+ H 0 +BAO constrains n s = 0.9538 ± 0.0081 in the ΛCDM model, a 5.7σ detection of n s < 1, and places an upper limit of r < 0.11 (95% C.L.) in the ΛCDM+ r model. These new constraints on n s and r have significant implications for our understanding of inflation, which we discuss in the context of selected single-field inflation models.