Showing papers by "L. P. L. Colombo published in 2003"

BaR-SPOrt: an experiment to measure the linearly polarized sky emission from both the cosmic microwave background and foregrounds

Abstract: The BaR-SPOrt experiment is aimed at measuring the polarization of the microwave sky at 32 and 90 GHz with sub-degree angular resolution. In this spectral and angular window it is possible to detect the polarization of the cosmic microwave background, which is one of the most ambitious goals of the today astrophysics. The experiment has been designed to fly onboard a Long Duration Balloon to be launched from polar regions, where it is possible to observe low foreground emission sky patches situated at high galactic latitudes.

Nature of Dark Energy and Polarization Measurements

Abstract: High sensitivity polarization measures, on wide angular scales, together with data on anisotropy, can be used to fix DE parameters. In this paper, first of all, we aim to determine the sensitivity needed to provide significant limits. Our analysis puts in evidence that there is a class of DE models that polarization measures can possibly exclude soon. This class includes models with DE due to a Ratra-Peebles (RP) potential. Using a likelihood analysis, we show that it is possible to distinguish RP models from LCDM and other dynamical DE models, already with the sensitivity of experiments like SPOrt or WMAP, thanks to their negative TE correlation at low-l, when the optical depth tau is sufficiently large. On the contrary, fixing the energy scale Lambda for RP potentials or distinguishing between LCDM and other DE potentials requires a much lower pixel noise, that no planned polarization experiment will achieve. While reviewing this paper after the referee report, the first-year WMAP data were released. WMAP finds large positive anisotropy-polarization correlations at low l; this apparently excludes DE models with RP potentials.

Constraining the reionization history with large angle CMB polarization

Abstract: The first-year WMAP data release showed that the reionization optical depth to CMB photons is greater than previously thought. This follows from unexpectedly high values of the C^TE_l spectrum, for l up to ~30, presumably allowing a measurement of the E-mode polarization spectrum C^E_l sooner than expected. This note aims to test the capability of large-angle polarization experiments to explore the history of the cosmological reionization, considering also the impact of cosmic variance. In particular, here we discuss how well the ionized fraction x_e and the reionization redshift z_r can be separately measured, at various levels of instrumental noise.