Parity in the CMB: Space Oddity

We search for a direction in the sky that exhibits parity symmetry under reflections through a plane. We use the natural estimator, which compares the power in even and odd $\ell+m$ multipoles, and apply minimal blind masking of outliers to the ILC map in order to avoid large errors in the reconstruction of multipoles. The multipoles of the cut sky are calculated both naively and by using the covariance inversion method and we estimate the significance of our results using $\Lambda$CDM simulations. Focusing on low multipoles, $2\leq \ell \leq \ell_{\max}$ with $\ell_{\max}=5,6$ or even 7, we find two perpendicular directions of even and odd parity in the map. While the even parity direction does not appear significant, the odd direction is quite significant -- at least a $3.6\sigma$ effect.Comment: 6 pages, 7 figures. Accepted for publication in The Astrophysical Journa

Estimates of multipolar coefficients to search for cosmic ray anisotropies with non-uniform or partial sky coverage

We study the possibility to extract the multipolar moments of an underlying distribution from a set of cosmic rays observed with non-uniform or even partial sky coverage. We show that if the degree is assumed to be upper bounded by $L$, each multipolar moment can be recovered whatever the coverage, but with a variance increasing exponentially with the bound $L$ if the coverage is zero somewhere. Despite this limitation, we show the possibility to test predictions of a model without any assumption on $L$ by building an estimate of the covariance matrix seen through the exposure function.Comment: 20 pages, 8 figure

The Planck-LFI instrument: analysis of the 1/f noise and implications for the scanning strategy

We study the impact of the 1/f noise on the PLANCK Low Frequency Instrument (LFI) osbervations (Mandolesi et al 1998) and describe a simple method for removing striping effects from the maps for a number of different scanning stategies. A configuration with an angle between telescope optical axis and spin-axis just less than 90 degrees (namely 85 degress) shows good destriping efficiency for all receivers in the focal plane, with residual noise degradation < 1-2 %. In this configuration, the full sky coverage can be achieved for each channel separately with a 5 degrees spin-axis precession to maintain a constant solar aspect angle.Comment: submitted to Astronomy and Astrophysics, 12 pages, 15 PostSript figure

A measurement of large-scale peculiar velocities of clusters of galaxies: results and cosmological implications

Peculiar velocities of clusters of galaxies can be measured by studying the fluctuations in the cosmic microwave background (CMB) generated by the scattering of the microwave photons by the hot X-ray emitting gas inside clusters. While for individual clusters such measurements result in large errors, a large statistical sample of clusters allows one to study cumulative quantities dominated by the overall bulk flow of the sample with the statistical errors integrating down. We present results from such a measurement using the largest all-sky X-ray cluster catalog combined to date and the 3-year WMAP CMB data. We find a strong and coherent bulk flow on scales out to at least > 300 h^{-1} Mpc, the limit of our catalog. This flow is difficult to explain by gravitational evolution within the framework of the concordance LCDM model and may be indicative of the tilt exerted across the entire current horizon by far-away pre-inflationary inhomogeneities.Comment: Ap.J. (Letters), in press. 20 Oct issue (Vol. 686