Constraints on Cosmology from the Cosmic Microwave Background Power Spectrum of the 2500 deg^{2} SPTSZ Survey
Abstract
We explore extensions to the ΛCDM cosmology using measurements of the cosmic microwave background (CMB) from the recent SPTSZ survey, along with data from WMAP7 and measurements of H _{0} 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 (dn_{s} /dln k), as well as two extensions that modify the damping tail power (the primordial helium abundance Y_{p} and the effective number of neutrino species N _{eff}) and one that modifies the largescale power due to the integrated SachsWolfe effect (the sum of neutrino masses ∑m _{ν}). These extensions have similar observational consequences and are partially degenerate when considered simultaneously. Of the six oneparameter extensions considered, we find CMB to have the largest preference for dn_{s} /dln k with 0.046 < dn_{s} /dln k < 0.003 at 95% confidence, which strengthens to a 2.7σ indication of dn_{s} /dln k < 0 from CMB+BAO+H _{0}. Detectable dn_{s} /dln k ≠ 0 is difficult to explain in the context of singlefield, slowroll inflation models. We find N _{eff} = 3.62 ± 0.48 for the CMB, which tightens to N _{eff} = 3.71 ± 0.35 from CMB+BAO+H _{0}. Larger values of N _{eff} relieve the mild tension between CMB, BAO, and H _{0}. When the SunyaevZel'dovich selected galaxy cluster abundances (SPT_{CL}) data are also included, we obtain N _{eff} = 3.29 ± 0.31. Allowing for ∑m _{ν} gives a 3.0σ detection of ∑m _{ν} > 0 from CMB+BAO+H _{0} +SPT_{CL}. 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 H _{0} show some preference for massive neutrinos; data combinations including H _{0} favor nonzero masses only if BAO data are also included. We also constrain the twoparameter extensions N _{eff} + ∑m _{ν} and N _{eff} + Y_{p} to explore constraints on additional light species and big bang nucleosynthesis, respectively.
 Publication:

The Astrophysical Journal
 Pub Date:
 February 2014
 DOI:
 10.1088/0004637X/782/2/74
 arXiv:
 arXiv:1212.6267
 Bibcode:
 2014ApJ...782...74H
 Keywords:

 cosmic background radiation;
 cosmological parameters;
 early universe;
 inflation;
 Astrophysics  Cosmology and Extragalactic Astrophysics
 EPrint:
 27 pages, 20 figures. Replaced with version accepted by ApJ