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Register a new userStatus of CMB Polarization Measurements from DASI and Other Experiments
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We review the current status and future plans for polarization measurements of the cosmic microwave background radiation, as well as the cosmology these measurements will address. After a long period of increasingly sensitive upper limits, the DASI experiment has detected the E-mode polarization and both the DASI and WMAP experiments have detected the TE correlation. These detections provide confirmation of the standard model of adiabatic primordial density fluctuations consistent with inflationary models. The WMAP TE correlation on large angular scales provides direct evidence of significant reionization at higher redshifts than had previously been supposed. These detections mark the beginning of a new era in CMB measurements and the rich cosmology that can be gleaned from them.
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We have simulated the interferometric observation of the Cosmic Microwave Background (CMB) temperature and polarization fluctuations. We have constructed data pipelines from the time-ordered raw visibility samples to the CMB power spectra which utilize the methods of data compression, maximum likelihood analysis, and optimal subspace filtering. They are customized for three observational strategies, such as the single pointing, the mosaicking, and the drift-scanning. For each strategy, derived are the optimal strategy parameters that yield band power estimates with minimum uncertainty. The results are general and can be applied to any close-packed array on a single platform such as the CBI and the forthcoming AMiBA experiments. We have also studied the effect of rotation of the array platform on the band power correlation by simulating the CBI single pointing observation. It is found that the band power anti-correlations can be reduced by rotating the platform and thus densely sampling the visibility plane. This enables us to increase the resolution of the power spectrum in the l-space down to the limit of the sampling theorem (Delta l = 226 = pi / theta), which is narrower by a factor of about sqrt{2} than the resolution limit (Delta l = 300) used in the recent CBI single pointing observation. The validity of this idea is demonstrated for a two-element interferometer that samples visibilities uniformly in the uv-annulus. From the fact that the visibilities are the Fourier modes of the CMB field convolved with the beam, a fast unbiased estimator (FUE) of the CMB power spectra is developed and tested. It is shown that the FUE gives results very close to those from the quadratic estimator method without requiring large computer resources even though uncertainties in the results increase.
We present an improved analysis of the final dataset from the QUaD experiment. Using an improved technique to remove ground contamination, we double the effective sky area and hence increase the precision of our CMB power spectrum measurements by ~30% versus that previously reported. In addition, we have improved our modeling of the instrument beams and have reduced our absolute calibration uncertainty from 5% to 3.5% in temperature. The robustness of our results is confirmed through extensive jackknife tests and by way of the agreement we find between our two fully independent analysis pipelines. For the standard 6-parameter LCDM model, the addition of QUaD data marginally improves the constraints on a number of cosmological parameters over those obtained from the WMAP experiment alone. The impact of QUaD data is significantly greater for a model extended to include either a running in the scalar spectral index, or a possible tensor component, or both. Adding both the QUaD data and the results from the ACBAR experiment, the uncertainty in the spectral index running is reduced by ~25% compared to WMAP alone, while the upper limit on the tensor-to-scalar ratio is reduced from r < 0.48 to r < 0.33 (95% c.l). This is the strongest limit on tensors to date from the CMB alone. We also use our polarization measurements to place constraints on parity violating interactions to the surface of last scattering, constraining the energy scale of Lorentz violating interactions to < 1.5 x 10^{-43} GeV (68% c.l.). Finally, we place a robust upper limit on the strength of the lensing B-mode signal. Assuming a single flat band power between l = 200 and l = 2000, we constrain the amplitude of B-modes to be < 0.57 micro-K^2 (95% c.l.).
Science opportunities and recommendations concerning optical/infrared polarimetry for the upcoming decade in the field of cosmology. Community-based White Paper to Astro2010 in response to the call for such papers.
BICEP1 is a millimeter-wavelength telescope designed specifically to measure the inflationary B-mode polarization of the Cosmic Microwave Background (CMB) at degree angular scales. We present results from an analysis of the data acquired during three seasons of observations at the South Pole (2006 to 2008). This work extends the two-year result published in Chiang et al. (2010), with additional data from the third season and relaxed detector-selection criteria. This analysis also introduces a more comprehensive estimation of band-power window functions, improved likelihood estimation methods and a new technique for deprojecting monopole temperature-to-polarization leakage which reduces this class of systematic uncertainty to a negligible level. We present maps of temperature, E- and B-mode polarization, and their associated angular power spectra. The improvement in the map noise level and polarization spectra error bars are consistent with the 52% increase in integration time relative to Chiang et al. (2010). We confirm both self-consistency of the polarization data and consistency with the two-year results. We measure the angular power spectra at 21 <= l <= 335 and find that the EE spectrum is consistent with Lambda Cold Dark Matter (LCDM) cosmology, with the first acoustic peak of the EE spectrum now detected at 15sigma. The BB spectrum remains consistent with zero. From B-modes only, we constrain the tensor-to-scalar ratio to r = 0.03+0.27-0.23, or r < 0.70 at 95% confidence level.
The polarization of the Cosmic Microwave Background (CMB)is a powerful observational tool at hand for modern cosmology. It allows to break the degeneracy of fundamental cosmological parameters one cannot obtain using only anisotropy data and provides new insight into conditions existing in the very early Universe. Many experiments are now in progress whose aim is detecting anisotropy and polarization of the CMB. Measurements of the CMB polarization are however hampered by the presence of polarized foregrounds, above all the synchrotron emission of our Galaxy, whose importance increases as frequency decreases and dominates the polarized diffuse radiation at frequencies below $simeq 50$ GHz. In the past the separation of CMB and synchrotron was made combining observations of the same area of sky made at different frequencies. In this paper we show that the statistical properties of the polarized components of the synchrotron and dust foregrounds are different from the statistical properties of the polarized component of the CMB, therefore one can build a statistical estimator which allows to extract the polarized component of the CMB from single frequency data also when the polarized CMB signal is just a fraction of the total polarized signal. This estimator improves the signal/noise ratio for the polarized component of the CMB and reduces from about 50 GHz to about 20 GHz the frequency above which the polarized component of the CMB can be extracted from single frequency maps of the diffuse radiation.
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