Article

A Measurement of the Damping Tail of the Cosmic Microwave Background Power Spectrum with the South Pole Telescope

The Astrophysical Journal (Impact Factor: 6.28). 05/2011; 743(1). DOI: 10.1088/0004-637X/743/1/28
Source: arXiv

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 square degrees of sky observed at 150 GHz during 2008 and
2009. Here we present the power spectrum over the multipole range 650 < ell <
3000, where it is dominated by primary CMB anisotropy. We combine this power
spectrum with the power spectra from the seven-year 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, LCDM cosmological model. The SPT+WMAP
constraint on the spectral index of scalar fluctuations is ns = 0.9663 +/-
0.0112. We detect, at ~5-sigma significance, the effect of gravitational
lensing on the CMB power spectrum, and find its amplitude to be consistent with
the LCDM cosmological model. We explore a number of extensions beyond the LCDM
model. Each extension is tested independently, although there are degeneracies
between some of the extension parameters. We constrain the tensor-to-scalar
ratio to be r < 0.21 (95% CL) and constrain the running of the scalar spectral
index to be dns/dlnk = -0.024 +/- 0.013. We strongly detect the effects of
primordial helium and neutrinos on the CMB; a model without helium is rejected
at 7.7-sigma, while a model without neutrinos is rejected at 7.5-sigma. The
primordial helium abundance is measured to be Yp = 0.296 +/- 0.030, and the
effective number of relativistic species is measured to be Neff = 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 ns = 0.9668 +/- 0.0093, r <
0.17 (95% CL), and Neff = 3.86 +/- 0.42. The SPT+WMAP data show...

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Available from: Antony A. Stark, Dec 22, 2014
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    • "We use the BBN PArthENoPE code [96] [97] to compute the helium abundance, Y P , for different values of Ω b h 2 , ∆N ef f , ξ ν and changes of neutron and proton interaction rates due to We adapt the latest version of the publicly available package CosmoMC [81] for our cosmological analysis and use the following datasets and likelihood codes: • The Planck CMB anisotropy angular power spectrum, combined with WMAP-9 year polarization power spectrum at low ℓ [82] and the corresponding codes [1] [83]: Commander, that computes the low-l Planck likelihood, CamSpec, that computes the Planck likelihood for 50 ≤ l ≤ 2500, LowLike, that computes the likelihoods for 2 ≤ l ≤ 32 polarization data and Lensing, that computes the likelihoods from Planck lensing power spectrum for 40 ≤ l ≤ 400 [84]. • The high-l CMB data from Atacama Cosmology Telescope(ACT) [85] [86] and the South Pole Telescope (SPT) [87] [88]. "
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    • "[71] [72] [73]. The latest CMB results of WMAP, SPT [74] and ACT [75] combined with BAO and HST gave N eff = 3.84 ± 0.40 at 68% C.L. [76]. Thus, although somehow controversial [77], rather than a constraint there seemed to be a 2-σ preference for a non-negligible amount of unaccounted dark radiation [78]. "
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