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M. Tucci

Publications and source records attributed to M. Tucci.

26 records · Page 2Linked to original sources
arXiv2004

Predictions on high frequency polarization properties of extragalactic radio sources and implications for CMB polarization measurements

We present a method to simulate the polarization properties of extragalactic radio sources at microwave frequencies. Polarization measurements of nearly 2x10^6 sources at 1.4 GHz are provided by the NVSS survey. Using this catalogue and the GB6 survey, we study the distribution of the polarization degree of both steep- and flat-spectrum sources. We find that the polarization degree is anti-correlated with the flux density for the former population, while no correlation is detected for the latter. The available high-frequency data are exploited to determine the frequency dependence of the distribution of polarization degrees. Using such information and the evolutionary model by Toffolatti et al. (1998), we estimate the polarization power spectrum of extragalactic radio sources at \geq 30 GHz and their contamination of CMB polarization maps. Two distinct methods to compute point-source polarization spectra are presented, extending and improving the one generally used in previous analyses. While extragalactic radio sources can significantly contaminate the CMB E-mode power spectrum only at low frequencies (<30 GHz), they can severely constrain the detectability of the CMB B-mode up to ~100 GHz.

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arXiv2003

An iterative destriping technique for diffuse background polarization data

We describe a simple but effective iterative procedure specifically designed to destripe Q and U Stokes parameter data as those collected by the SPOrt experiment onboard the International Space Station (ISS). The method is general enough to be useful for other experiments, both in polarization and total intensity. The only requirement for the algorithm to work properly is that the receiver knee frequency must be lower than the signal modulation frequency, corresponding in our case to the ISS orbit period. Detailed performances of the technique are presented in the context of the SPOrt experiment, both in terms of added rms noise and residual correlated noise.

astro-ph↗
arXiv2003

The BaR-SPOrt Experiment

BaR-SPOrt (Balloon-borne Radiometers for Sky Polarisation Observations) is an experiment to measure the linearly polarized emission of sky patches at 32 and 90 GHz with sub-degree angular resolution. It is equipped with high sensitivity correlation polarimeters for simultaneous detection of both the U and Q stokes parameters of the incident radiation. On-axis telescope is used to observe angular scales where the expected polarization of the Cosmic Microwave Background (CMBP) peaks. This project shares most of the know-how and sophisticated technology developed for the SPOrt experiment onboard the International Space Station. The payload is designed to flight onboard long duration stratospheric balloons both in the Northern and Southern hemispheres where low foreground emission sky patches are accessible. Due to the weakness of the expected CMBP signal (in the range of microK), much care has been spent to optimize the instrument design with respect to the systematics generation, observing time efficiency and long term stability. In this contribution we present the instrument design, and first tests on some components of the 32 GHz radiometer.

astro-ph↗
arXiv2002

SPOrt: an Experiment Aimed at Measuring the Large Scale Cosmic Microwave Background Polarization

SPOrt (Sky Polarization Observatory) is a space experiment to be flown on the International Space Station during Early Utilization Phase aimed at measuring the microwave polarized emission with FWHM = 7deg, in the frequency range 22-90 GHz. The Galactic polarized emission can be observed at the lower frequencies and the polarization of Cosmic Microwave Background (CMB) at 90 GHz, where contaminants are expected to be less important. The extremely low level of the CMB Polarization signal (< 1 uK) calls for intrinsically stable radiometers. The SPOrt instrument is expressly devoted to CMB polarization measurements and the whole design has been optimized for minimizing instrumental polarization effects. In this contribution we present the receiver architecture based on correlation techniques, the analysis showing its intrinsic stability and the custom hardware development carried out to detect such a low signal.

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arXiv2002

Polarization angular spectra of Galactic synchrotron emission on arcminute scales

We study the angular power spectra of the polarized component of the Galactic synchrotron emission in the 28-deg^2 Test Region of the Southern Galactic Plane Survey at 1.4 GHz. These data were obtained by the Australia Telescope Compact Array and allow us to investigate angular power spectra down to arcminute scales. We find that, at this frequency, the polarization spectra for E- and B-modes seem to be affected by Faraday rotation produced in compact foreground screens. A different behavior is shown by the angular spectrum of the polarized intensity PI=\sqrt{Q^2+U^2}. This is well fitted by a power law with slope \~1.7, which agrees with higher frequency results and can probably be more confidently extrapolated to the cosmological window.

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arXiv2000

The angular power spectra of polarized Galactic synchrotron

We derive the angular power spectra of intensity and polarization of Galactic synchrotron emission in the range 36 < l < 10^3 from the Parkes survey mapping the southern Galactic plane at 2.4 GHz. The polarization spectra of both electric and magnetic parity up to l \simeq 10^3 are approximated very well by power laws with slope coefficients \simeq 1.4, quite different from the CMB spectra. We show that no problem should arise from Galactic synchrotron for measurements of CMB polarization in the cosmological window.

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arXiv1996

Statistical Tests for CHDM and \LambdaCDM Cosmologies

We apply several statistical estimators to high-resolution N-body simulations of two currently viable cosmological models: a mixed dark matter model, having $Ω_ν=0.2$ contributed by two massive neutrinos (C+2\nuDM), and a Cold Dark Matter model with Cosmological Constant (\LambdaCDM) with $Ω_0=0.3$ and h=0.7. Our aim is to compare simulated galaxy samples with the Perseus-Pisces redshift survey (PPS). We consider the n-point correlation functions (n=2-4), the N-count probability functions P_N, including the void probability function P_0, and the underdensity probability function U_ε(where εfixes the underdensity threshold in percentage of the average). We find that P_0 (for which PPS and CfA2 data agree) and P_1 distinguish efficiently between the models, while U_εis only marginally discriminatory. On the contrary, the reduced skewness and kurtosis are, respectively, S_3\simeq 2.2 and S_4\simeq 6-7 in all cases, quite independent of the scale, in agreement with hierarchical scaling predictions and estimates based on redshift surveys. Among our results, we emphasize the remarkable agreement between PPS data and C+2\nuDM in all the tests performed. In contrast, the above \LambdaCDM model has serious difficulties in reproducing observational data if galaxies and matter overdensities are related in a simple way.

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