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 ℓ2Cℓ/2π of the thermal SZ power spectrum at 148 GHz is measured to be 3.4±1.4 μK2 at ℓ = 3000, while the corresponding amplitude of the kinematic SZ power spectrum has a 95% confidence level upper limit of 8.6 μK2. 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 Neff = 2.79±0.56, in agreement with the canonical value of Neff = 3.046 for three massless neutrinos. We constrain the sum of the neutrino masses to be Σmν < 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 Yp = 0.225±0.034, and measure no variation in the fine structure constant α since recombination, with α/α0 = 1.004±0.005. We also find no evidence for any running of the scalar spectral index, dns/dln k = −0.004±0.012.
Highlights
We find that fixing the primordial power to be scale invariant and combining all CMB data (WMAP7+Atacama Cosmology Telescope (ACT)+South Pole Telescope (SPT)+ACTDefl) with Baryon Acoustic Oscillations (BAO) and the H0 measurement yields a constraint on the string amplitude of qstr = 0.005, or Gμ = 7.1 × 10−8 (95% CL)
In the ACT analysis, using only the 1-year data, (Dunkley et al 2011) we modeled the SZ power spectrum using only a total amplitude of the SZ signal, which was constrained relative to a theoretical spectrum with σ8 = 0.8 as aSZ/aSZ,σ8=0.8 = 0.85 ± 0.26 using both 148 GHz and 218 GHz frequency bands, and which can be interpreted as l(l + 1)/2πCltotSZ = 6.8 ± 2.9 μK2 at l = 3000 using the Battaglia et al (2010) template
The solid curves are for the ACT data in combination with WMAP7 data, the light dotted green curves are for SPT+WMAP7, under the assumption of priors on the thermal SZ (tSZ)-Cosmic Infrared Background (CIB) correlation of ξ < 0.5 (ξ < 0.2)
Summary
Studies of the cosmic microwave background (CMB) have dramatically progressed over the past two decades (e.g., Smoot et al 1992; Cheng et al 1997; Baker et al 1999; Miller et al 1999; de Bernardis et al 2000; Knox & Page 2000; Hanany et al 2000; Lee et al 2001; Romeo et al 2001; Netterfield et al 2002; Halverson et al 2002; Kovac et al 2002; Carlstrom et al 2003; Pearson et al 2003; Scott et al 2003; Benoıt et al 2003; Spergel et al 2003; Johnson et al 2007; Chiang et al 2010). The Atacama Cosmology Telescope (ACT) complements measurements from WMAP by observing from l ≃ 300 to l = 10000 This widens the range of data available to constrain both cosmological parameters through the Silk damping tail of the primary CMB (Silk 1968) and the residual power from secondary sources between us and the surface of last scattering. These sources include galaxy clusters, which are detectable at microwave frequencies through the Sunyaev-Zel’dovich (SZ) effect (Zel’dovich & Sunyaev 1969; Sunyaev & Zel’dovich 1970). The solid line indicates the best-fit cosmological model including foreground emission, while the dashed line shows the best-fit primordial CMB spectrum This binning was selected for the common analysis of the equatorial and southern data. The cross-correlation calibration method is described in Hajian et al (2012); details of the calibration of the ACT 3-year data are given in Das et al (2013)
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