The Atacama Cosmology Telescope: Cosmological parameters from three seasons of data

Abstract

We present constraints on cosmological and astrophysical parameters from high-resolution microwave background maps at 148 GHz and 218 GHz made by the Atacama Cosmology Telescope (ACT) in three seasons of observations from 2008 to 2010. A model of primary cosmological and secondary foreground parameters is fit to the map power spectra and lensing deflection power spectrum, including contributions from both the thermal Sunyaev-Zeldovich (tSZ) effect and the kinematic Sunyaev-Zeldovich (kSZ) effect, Poisson and correlated anisotropy from unresolved infrared sources, radio sources, and the correlation between the tSZ effect and infrared sources. The power 2 C /2π of the thermal SZ power spectrum at 148 GHz is measured to be 3.4 ± 1.4 µK 2 at = 3000, while the corresponding amplitude of the kinematic SZ power spectrum has a 95% confidence level upper limit of 8.6 µK 2 . Combining ACT power spectra with the WMAP 7-year temperature and polarization power spectra, we find excellent consistency with the LCDM model. We constrain the number of effective relativistic degrees of freedom in the early universe to be N eff = 2.79 ± 0.56, in agreement with the canonical value of N eff = 3.046 for three massless neutrinos. We constrain the sum of the neutrino masses to be Σm ν < 0.39 eV at 95% confidence when combining ACT and WMAP 7-year data with BAO and Hubble constant measurements. We constrain the amount of primordial helium to be Y p = 0.225 ± 0.034, and measure no variation in the fine structure constant α since recombination, with α/α 0 = 1.004 ± 0.005. We also find no evidence for any running of the scalar spectral index, dn s /d ln k = −0.004 ± 0.012.

Light inflaton after LHC8 and WMAP9 results

“…Another issue has risen due to the recent analyses of cosmological data, mainly observations of the Cosmic Microwave Background (CMB) anisotropy by SPT [10], ACT [11], and the common global fit together with the analysis of CMB data collected for 9 years by WMAP [12]. The most important, relevant for our model result is lowering an upper limit on the tensor-to-scalar perturbations ratio, which excludes the simple chaotic inflation with quartic potential discussed above at more than 95% confidence level.…”

Evading the Lyth bound in hybrid natural inflation

“…Cosmological inflation [1][2][3][4], and in particular the generation of curvature perturbations through quantum fluctuations of the inflaton field [5][6][7][8][9], allows for a surprisingly accurate description of recent Planck data [10,11] (see also [12][13][14]). Concrete field-theoretic realizations roughly fall in two classes: large-field and small-field models.…”

Dark energy imprints on the kinematic Sunyaev–Zel'dovich signal

“…By comparing the constraints from [47], [25] and [48], we can see that although the constraints are not very strong at current situation, the SPT constraint with bispectrum (black data point on Fig. 8b) already tend to rule out the model with (w 0 = −0.8, w a = 0.5).…”

“…Now we put together the factors of structure growth, comoving distance, and power spectrum of curl momentum field to analyze how dark energy affects the kSZ angular power spectrum. (95% confidence level) from Atacama Cosmology Telescope (ACT) [47] and D ℓ=3000 ≤ 6.7µK 2 (95% CL) from South Pole Telescope (SPT1) [25]. The black data point shows D ℓ=3000 = 2.9 ± 1.5µK 2 (1σ CL) also from South Pole Telescope (SPT2) while including bispectrum constraints [48].…”

“…We now discuss what current and future observational constraints can be obtained on the kSZ power spectrum and its prospective to constrain dark energy. In [47], by using 148 GHz and 218 GHz Atacama Cosmology Telescope (ACT) data and fitting the template with contribution from thermal and kinetic SZ effects, infrared sources and radio sources, the 95% level upper limit is found to be 8.6µK 2 . In [25], the constraint on D ℓ=3000 is obtained by combining 95, 150 and 220 GHz channel data of SPT.…”