CONSTRAINTS ON COSMOLOGY FROM THE COSMIC MICROWAVE BACKGROUND POWER SPECTRUM OF THE 2500 deg2 SPT-SZ SURVEY

By Z. Hou, C. Reichardt, K. Story, B. Follin, R. Keisler, K. Aird, B. Benson, L. Bleem, J. Carlstrom, C. Chang and 42 more. 2012

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We explore extensions to the ΛCDM cosmology using measurements of the cosmic microwave background (CMB) from the recent SPT-SZ survey, along with data from WMAP7 and measurements of H0 and baryon acoustic oscillation (BAO). We check for consistency within ΛCDM between these data sets, and find some tension. The CMB alone gives weak support to physics beyond ΛCDM, due to a slight trend relative to ΛCDM of decreasing power toward smaller angular scales. While it may be due to statistical fluctuation, this trend could also be explained by several extensions. We consider running of the primordial spectral index (dns/dln k), as well as two extensions that modify the damping tail power (the primordial helium abundance Yp and the effective number of neutrino species Neff) and one that modifies the large-scale power due to the integrated Sachs–Wolfe effect (the sum of neutrino masses ∑mν). These extensions have similar observational consequences and are partially degenerate when considered simultaneously. Of the six one-parameter extensions considered, we find CMB to have the largest preference for dns/dln k with −0.046 < dns/dln k < −0.003 at 95% confidence, which strengthens to a 2.7σ indication of dns/dln k < 0 from CMB+BAO+H0. Detectable dns/dln k ≠ 0 is difficult to explain in the context of single-field, slow-roll inflation models. We find Neff = 3.62 ± 0.48 for the CMB, which tightens to Neff = 3.71 ± 0.35 from CMB+BAO+H0. Larger values of Neff relieve the mild tension between CMB, BAO, and H0. When the Sunyaev–Zel'dovich selected galaxy cluster abundances () data are also included, we obtain Neff = 3.29 ± 0.31. Allowing for ∑mν gives a 3.0σ detection of ∑mν > 0 from CMB+BAO+H0 +. The median value is (0.32 ± 0.11) eV, a factor of six above the lower bound set by neutrino oscillation observations. All data sets except H0 show some preference for massive neutrinos; data combinations including H0 favor nonzero masses only if BAO data are also included. We also constrain the two-parameter extensions Neff + ∑mν and Neff + Yp to explore constraints on additional light species and big bang nucleosynthesis, respectively.

Subfields: Astronomy and Astrophysics, Nuclear and High Energy Physics

View Paper: https://www.semanticscholar.org/paper/4054b96b78207fed7e5377dac9559e530cc553d6

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Citations in the corpus

New light species and the CMB (2013, methodology): “ but consistent excess in the measured value of g∗ [17–20]. Prior to the results from the Planck satellite, the most precise reported measurement was g∗ = 3.69±0.16, corresponding to Neff = 3.71±0.35 [19], coming from a combination of data from the South Pole Telescope (SPT) and the Wilkinson Microw”
Detection of B-mode polarization at degree angular scales by BICEP2. (2014, methodology): “…in striking concordance with predictions of ΛCDM and constraining its key parameters to sub-percent precision (e.g. Bennett et al. 2013; Hinshaw et al. 2013; Story et al. 2013; Hou et al. 2014; Sievers et al. 2013; Das et al. 2013; Planck Collaboration XV 2013; Planck Collaboration XVI 2013).”
The Phenomenology of Right Handed Neutrinos (2013, result): “n experiments [84]; most of the region favoured by LNSD is excluded by ICARUS, KARMEN and MiniBooNE. On the other hand, there is also tension between the latest results from the CMB. SPT+WMAP results [292] favour DR with Neﬀ = 3.62 ± 0.48; this is consistent with the Neﬀ ≃ 4 predicted by a thermaliz”