Point sources in the MAP sky maps

We discuss point sources foregrounds for the MAP experiment. We consider several possible strategies for removing them and we assess how the statistics of the CMB signal are affected by the residual sources. Assuming a power law distribution for the point sources, we propose a method aimed to determine the slope of the distribution from the analysis of the moments of the observed maps. The same method allows for a determination of the underlying CMB variance. We conclude that the best strategy for point sources finding is the simultaneous thresholding of the filtered map at all frequencies, with a relatively low threshold. With this strategy, we expect to find 70 (95)% of the sources above 3 (4) $\sigma$. Assuming the most conservative case for point sources detection, the recovered slope of the point sources distribution is $2.55 \pm 0.15$, for a fiducial $n=2.5$ value. The recovered CMB pus noise map variance is within 0.2% from the real one, with a standard deviation of $0.31$, while Cosmic variance contributes 2.2% to the same CMB plus noise map.Comment: 21 pages, 8 figures. Submitted to Ap

Early Universe models from Noncommutative Geometry

We investigate cosmological predictions on the early universe based on the noncommutative geometry models of gravity coupled to matter. Using the renormalization group analysis for the Standard Model with right handed neutrinos and Majorana mass terms, which is the particle physics content of the most recent noncommutative geometry models, we analyze the behavior of the coefficients of the gravitational and cosmological terms in the Lagrangian derived from the asymptotic expansion of the spectral action functional of noncommutative geometry. We find emergent Hoyle-Narlikar and conformal gravity at the see-saw scales and a running effective gravitational constant, which affects the propagation of gravitational waves and the evaporation law of primordial black holes and provides Linde models of negative gravity in the early universe. The same renormalization group analysis also governs the running of the effective cosmological constant of the model. The model also provides a Higgs based slow-roll inflationary mechanism, for which one can explicitly compute the slow-roll parameters. The particle physics content allows for dark matter models based on sterile neutrinos with Majorana mass terms.Comment: 49 pages, LaTeX, 26 pdf figure

Accretion flows in early-type galaxies and CMB experiments

We investigate the possible contribution from the emission of accretion flows around supermassive black holes in early type galaxies to current measurements of the Cosmic Microwave Background (CMB) at radio frequencies. We consider a range of luminosities suggested by targeted radio observations and accretion models and compute the residual contribution of these sources to the spectrum and bispectrum of the observed CMB maps. As for high-resolution CMB experiments, we find that the unresolved component of these sources could make up to ~40-50% of the observed CBI and BIMA power spectrum at l > 2000. As a consequence, the inferred sigma_8^{SZ} value could be biased high by up to 6-7%. As for all sky experiments, we find that the contribution of accretion-flow sources to the WMAP bispectrum is at the 2-3 per cent level at most. At the flux limit that Planck will achieve, however, these sources may contribute up to 15 per cent of the bispectrum in the 60-100 GHz frequency range. Moreover, Planck should detect hundreds of these sources in the 30-300 GHz frequency window. These detections, possibly coupled with galaxy type confirmation from optical surveys, will allow number counts to put tighter constraints on early-type galaxies radio luminosity and accretion flows properties. These sources may also contribute up to the 30 per cent level to the residual radio sources power spectrum in future high-resolution SZ surveys (like ACT or APEX) reaching mJy flux limits.Comment: 7 pages, 3 figures, accepted to MNRA

A Characteristic Scale on the Cosmic Microwave Sky

The current suite of results from Cosmic Microwave Background anisotropy experiments is fulfilling the promise of providing extraordinary levels of discrimination between cosmological models. We calculate a binned anisotropy power spectrum, which we tabulate, along with error bars and bin-to-bin correlations, so that it can be easily used for constraining models. The resulting power spectrum is flat at large angles, with a gradual rise to a prominent peak at around 0.5 degrees and a decrease thereafter. This is precisely the shape predicted by inflationary-inspired adiabatic models. Within that class of cosmologies, this characteristic scale imprinted on the CMB sky can be used to infer that the geometry of the Universe is very close to flat. The next wave of CMB results should add fuel to the debate about whether or not the Universe once inflated, as well as beginning in earnest the task of measuring cosmological parameters.Comment: 6 pages, 1 figure. A less technical article based on the same work has appeared in Science Perspectives under the title "How Flat is the Universe?" (Science, Mar 24, 2000, 2171-2172

Probing the largest scale structure in the universe with polarization map of galaxy clusters

We introduce a new formalism to describe the polarization signal of galaxy clusters on the whole sky. We show that a sparsely sampled, half-sky map of the cluster polarization signal at $z\sim 1$ would allow to better characterize the very large scale density fluctuations. While the horizon length is smaller in the past, two other competing effects significantly remove the contribution of the small scale fluctuations from the quadrupole polarization pattern at $z\sim 1$. For the standard Lambda-CDM universe with vanishing tensor mode, the quadrupole moment of the temperature anisotropy probed by WMAP is expected to have a ~32% contribution from fluctuations on scales below 6.3h^{-1}Gpc. This percentage would be reduced to ~2% level for the quadrupole moment of polarization pattern at $z\sim 1$. A cluster polarization map at $z \sim 1$ would shed light on the potentially anomalous features of the largest scale structure in the observable universe.Comment: 5 pages, 2 figures, revised version, to appear in PR