A Measurement of the Damping Tail of the Cosmic Microwave Background Power Spectrum with the South Pole Telescope
Abstract
We present a measurement of the angular power spectrum of the cosmic microwave background (CMB) using data from the South Pole Telescope (SPT). The data consist of 790 deg^{2} of sky observed at 150 GHz during 2008 and 2009. Here we present the power spectrum over the multipole range 650 < l < 3000, where it is dominated by primary CMB anisotropy. We combine this power spectrum with the power spectra from the sevenyear Wilkinson Microwave Anisotropy Probe (WMAP) data release to constrain cosmological models. We find that the SPT and WMAP data are consistent with each other and, when combined, are well fit by a spatially flat, ΛCDM cosmological model. The SPT+WMAP constraint on the spectral index of scalar fluctuations is n_{s} = 0.9663 ± 0.0112. We detect, at ~5σ significance, the effect of gravitational lensing on the CMB power spectrum, and find its amplitude to be consistent with the ΛCDM cosmological model. We explore a number of extensions beyond the ΛCDM model. Each extension is tested independently, although there are degeneracies between some of the extension parameters. We constrain the tensortoscalar ratio to be r < 0.21 (95% CL) and constrain the running of the scalar spectral index to be dn_{s} /dln k = 0.024 ± 0.013. We strongly detect the effects of primordial helium and neutrinos on the CMB; a model without helium is rejected at 7.7σ, while a model without neutrinos is rejected at 7.5σ. The primordial helium abundance is measured to be Y_{p} = 0.296 ± 0.030, and the effective number of relativistic species is measured to be N _{eff} = 3.85 ± 0.62. The constraints on these models are strengthened when the CMB data are combined with measurements of the Hubble constant and the baryon acoustic oscillation feature. Notable improvements include n_{s} = 0.9668 ± 0.0093, r < 0.17 (95% CL), and N _{eff} = 3.86 ± 0.42. The SPT+WMAP data show a mild preference for low power in the CMB damping tail, and while this preference may be accommodated by models that have a negative spectral running, a high primordial helium abundance, or a high effective number of relativistic species, such models are disfavored by the abundance of lowredshift galaxy clusters.
 Publication:

The Astrophysical Journal
 Pub Date:
 December 2011
 DOI:
 10.1088/0004637X/743/1/28
 arXiv:
 arXiv:1105.3182
 Bibcode:
 2011ApJ...743...28K
 Keywords:

 cosmic background radiation;
 cosmological parameters;
 cosmology: observations;
 Astrophysics  Cosmology and Nongalactic Astrophysics
 EPrint:
 23 pages, 13 figures. Replaced with version accepted by ApJ. Data products are available at http://pole.uchicago.edu/public/data/keisler11/index.html or http://lambda.gsfc.nasa.gov/product/spt/spt_spectra_2011_get.cfm