Multiple Methods for Estimating the Bispectrum of the Cosmic Microwave Background with Application to the MAXIMA Data
نویسندگان
چکیده
We describe different methods for estimating the bispectrum of Cosmic Microwave Background data. In particular we construct a minimum variance estimator for the flat-sky limit and compare results with previously-studied frequentist methods. Application to the MAXIMA dataset shows consistency with primordial Gaussianity. Weak quadratic non-Gaussianity is characterised by a tunable parameter fNL, corresponding to non-Gaussianity at a level ∼ 10−5fNL (ratio of non-Gaussian to Gaussian terms), and we find limits of |fNL| < 950 for the minimum-variance estimator and |fNL| < 1650 for the usual frequentist estimator. These are the tightest limits on primordial non-Gaussianity which include the full effects of the radiation transfer function.
منابع مشابه
Estimating non-gaussianity in the microwave background
The bispectrum of the microwave background sky is a possible discriminator between inflationary and defect models of structure formation in the Universe. The bispectrum, which is the analogue of the temperature 3-point correlation function in harmonic space, is zero for most inflationary models, but non-zero for non-gaussian models. The expected departures from zero are small, and easily masked...
متن کاملAN ESTIMATE OF THE PRIMORDIAL NON-GAUSSIANITY PARAMETER fNL USING THE NEEDLET BISPECTRUM FROM WMAP
We use the full bispectrum of spherical needlets applied to the WMAP data of the cosmic microwave background as an estimator for the primordial non-Gaussianity parameter fNL. We use needlet scales up to lmax = 1000 and the KQ75 galactic cut and find fNL = 84 ± 40 corrected for point source bias. We also introduce a set of consistency tests to validate our results against the possible influence ...
متن کاملImprint of Reionization on the Cosmic Microwave Background Bispectrum
We study contributions to the cosmic microwave background (CMB) bispectrum from non-Gaussianity induced by secondary anisotropies during reionization. Large-scale structure in the reionized epoch both gravitational lenses CMB photons and produces Doppler shifts in their temperature from scattering off electrons in infall. The resulting correlation is potentially observable through the CMB bispe...
متن کاملFull-sky correlations of peaks in the microwave background
We compute precise predictions for the two-point correlation function of local maxima (or minima) in the temperature of the microwave background, under the assumption that it is a random gaussian field. For a given power spectrum and peak threshold there are no adjustable parameters, and since this analysis does not make the smallangle approximation of Heavens & Sheth (1999), it is essentially ...
متن کاملImproved simulation of non–Gaussian temperature and polarization CMB maps
We describe an algorithm to generate temperature and polarization maps of the cosmic microwave background radiation containing non–Gaussianity of arbitrary local type. We apply an optimized quadrature scheme that allows us to predict and control integration accuracy, speed up the calculations, and reduce memory consumption by an order of magnitude. We generate 1000 non– Gaussian CMB temperature...
متن کامل