The Atacama Cosmology Telescope: CMB polarization at 200 < ℓ < 9000
2014
We report on measurements of the
cosmic microwave background(CMB) and celestial polarization at 146 GHz made with the
Atacama Cosmology Telescope
Polarimeter(ACTPol) in its first three months of observing. Four regions of sky covering a total of 270
square degreeswere mapped with an angular resolution of 1.3'. The map noise levels in the four regions are between 11 and 17 μK-arcmin. We present TT, TE, EE, TB, EB, and BB power spectra from three of these regions. The observed E-mode polarization power spectrum, displaying six acoustic peaks in the range 200 < l < 3000, is an excellent fit to the prediction of the best-fit cosmological models from WMAP9+ACT and Planck data. The polarization power spectrum, which mainly reflects
primordialplasma velocity perturbations, provides an independent determination of cosmological parameters consistent with those based on the temperature power spectrum, which results mostly from
primordialdensity perturbations. We find that without masking any point sources in the EE data at l < 9000, the Poisson tail of the EE power spectrum due to polarized point sources has an amplitude less than 2.4 μ {sup 2} at l = 3000 at 95% confidence. Finally, we report that the
Crab Nebula, an important polarization calibration source at microwavemore » frequencies, has 8.7% polarization with an angle of 150.7{sup o} ± 0.6{sup o} when smoothed with a 5' Gaussian beam.« less
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