K. M. Górski

Master of the cosmic microwave background anisotropy power spectrum: a fast method for statistical analysis of large and complex cosmic microwave background data sets

We describe a fast and accurate method for estimation of the cosmic microwave background (CMB) anisotropy angular power spectrum—Monte Carlo Apodized Spherical Transform Estimator (MASTER). Originally devised for use in the interpretation of the BOOMERANG experimental data, MASTER is both a computationally efficient method suitable for use with the currently available CMB data sets (already large in size, despite covering small fractions of the sky, and affected by inhomogeneous and correlated noise) and a very promising application for the analysis of very large future CMB satellite mission products.

Measurement of the cosmic microwave background bispectrum on the COBE DMR sky maps

We measure the angular bispectrum of the cosmic microwave background (CMB) radiation anisotropy from the COBE Differential Microwave Radiometer (DMR) 4 yr sky maps. The angular bispectrum is the harmonic transform of the three-point correlation function, analogous to the angular power spectrum, the harmonic transform of the two-point correlation function. First, we study statistical properties of the bispectrum and the normalized bispectrum. We find the latter more useful for statistical analysis; the distribution of the normalized bispectrum is very much Gaussian, while the bare bispectrum distribution is highly non-Gaussian. Then, we measure 466 modes of the normalized bispectrum, all independent combinations of three-point configurations up to a maximum multipole of 20, the mode corresponding to the DMR beam size. By measuring 10 times as many modes as the sum of previous work, we test the Gaussianity of the DMR maps. We compare the data with the simulated Gaussian realizations, finding no significant detection of the normalized bispectrum on a mode-by-mode basis. We also find that the previously reported detection of the normalized bispectrum is consistent with a statistical fluctuation. By fitting a theoretical prediction to the data for the primordial CMB bispectrum, which is motivated by slow-roll inflation, we put a weak constraint on the parameter characterizing nonlinearity in inflation. Simultaneously fitting the foreground bispectra estimated from interstellar dust and synchrotron template maps shows that neither dust nor synchrotron emission significantly contributes to the bispectrum at high Galactic latitude. We conclude that the DMR map is consistent with Gaussianity.

Cosmic microwave background anisotropy power spectrum statistics for high precision cosmology

As the era of high precision cosmology approaches, the empirically determined power spectrum of the microwave background anisotropy

The Planck-LFI instrument: Analysis of the

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will provide a crucial test for cosmological theories. We present an exact semi-analytic framework for the study of the ampling statistics of the

noise and implications for the scanning strategy

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Resolving gravitational microlensing events with long-baseline optical interferometry Prospects for the ESO Very Large Telescope Interferometer

resulting from observations with partial sky coverage and anisotropic noise distributions. This includes space-borne, air-borne and ground-based experiments. We apply this theory to demonstrate its power for constructing fast but unbiased approximate methods for the joint estimation of cosmological parameters. Further applications, such as a test for possible non-Gaussianity of the underlying theory and a ``poor mans power spectrum estimator are suggested. An appendix derives recursion relations for the efficient computation of the couplings between spherical harmonics on the cut sky.

The Trispectrum of the 4 Year COBE DMR Data

We study the impact of noise on the Planck Low Frequency Instrument (LFI) observations (Mandolesi etxa0al.u2009 ) and describe a simple method for removing striping effects from the maps for a number of different scanning strategies. A configuration with an angle between telescope optical axis and spin-axis just less than 90° (namely ) shows good destriping efficiency for all receivers in the focal plane, with residual noise degradation . In this configuration, the full sky coverage can be achieved for each channel separately with a 5° spin-axis precession to maintain a constant solar aspect angle.

All-Sky Convolution for Polarimetry Experiments

Until now, the detailed interpretation of the observed microlensing events has suered from the fact that the physical parameters of the phenomenon cannot be uniquely determined from the available astronomical measurements, i.e. the photometric lightcurves. The situation will change in the near-future with the availability of long-baseline, sensitive optical interferometers, which should be able to resolve the images of the lensed objects into their components. For this, it will be necessary to achieve a milliarcsecond resolution on sources with typical magnitudes K> 12. Indeed, brighter events have never been observed up to now by micro-lensing surveys. We discuss the possibilities opened by the use of long baseline interferometry in general, and in particular for one such facility, the ESO VLT Interferometer, which will attain the required performance. We discuss the expected accuracy and limiting magnitude of such measurements. On the basis of the database of the events detected by the OGLE experiment, we estimate the number of microlenses that could be available for measurements by the VLTI. We nd that at least several tens of events could be observed each year. In conjunction with the photometric data, our ability to measure the angular separation between the microlensed images will enable a direct and unambiguous determination of both their masses and locations.

PLANCK LFI: Comparison between Galaxy Straylight Contamination and other systematic effects

We propose an estimator for the trispectrum of a scalar random field on a sphere, discuss its geometrical and statistical properties, and outline its implementation. By estimating the trispectrum of the 4 yr COBE Differential Microwave Radiometer experiment data (in HEALPix pixelization), we find new evidence of a non-Gaussian signal associated with a known systematic effect. We find that by removing data from the sky maps for those periods of time perturbed by this effect, the amplitudes of the trispectrum coefficients become completely consistent with predictions for a Gaussian sky. These results reinforce the importance of statistical methods based in harmonic space for quantifying non-Gaussianity.