Detection of polarization in the cosmic microwave background using DASI

Abstract

We report the detection of polarized anisotropy in the Cosmic Microwave Background radiation with the Degree Angular Scale Interferometer (DASI), located at the Amundsen-Scott South Pole research station. Observations in all four Stokes parameters were obtained within two 34 FWHM fields separated by one hour in Right Ascension. The fields were selected from the subset of fields observed with DASI in 2000 in which no point sources were detected and are located in regions of low Galactic synchrotron and dust emission. The temperature angular power spectrum is consistent with previous measurements and its measured frequency spectral index is −0.01 (−0.16 -0.14 at 68% confidence), where 0 corresponds to a 2.73 K Planck spectrum. The power spectrum of the detected polarization is consistent with theoretical predictions based on the interpretation of CMB anisotropy as arising from primordial scalar adiabatic fluctuations. Specifically, E-mode polarization is detected at high confidence (4.9σ). Assuming a shape for the power spectrum consistent with previous temperature measurements, the level found for the E-mode polarization is 0.80 (0.56 -1.10), where the predicted level given previous temperature data is 0.9 -1.1. At 95% confidence, an upper limit of 0.59 is set to the level of B-mode polarization with the same shape and normalization as the E-mode spectrum. The T E correlation of the temperature and E-mode polarization is detected at 95% confidence, and also found to be consistent with predictions. These results provide strong validation of the underlying theoretical framework for the origin of CMB anisotropy and lend confidence to the values of the cosmological parameters that have been derived from CMB measurements.

Summary of cosmology workshop

“…The level of polarization of the CMB being about a tenth of the temperature fluctuation, it is only very recently that the angular power spectrum of CMB polarization field has been detected. The Degree Angular Scale Interferometer (DASI) has measured the CMB polarization spectrum over limited band of angular scales in late 2002 [16]. The WMAP mission has also detected CMB polarization [17].…”

The current status of observational cosmology

“…For example, it is only very recently that the angular power spectrum of CMB polarization has been detected. The degree angular scale interferometer (DASI) has measured the CMB polarization spectrum over a limited band of angular scales (l ∼ 200-440) in late 2002 [20]. The WMAP mission has also detected CMB polarization [21].…”

Cosmological Parameters

“…The Atacama Cosmology Telescope (ACT) and South Pole Telescope (SPT) experiments extend these results to higher angular resolution, though without full-sky coverage. The most comprehensive measurements of CMB polarization come from the WMAP satellite final (9-year) data release [3], giving the spectrum of E-polarization anisotropies and the correlation spectrum between temperature and polarization (those spectra having first been detected by DASI [27]) . These are consistent with models based on the parameters we have described, and provide accurate determinations of many of those parameters [2].…”