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We present observations and cosmic microwave background (CMB) foreground analysis of the Parkes Galactic Meridian Survey, an investigation of the Galactic latitude behaviour of the polarized synchrotron emission at 2.3 GHz with the Parkes Radio Telescope. The survey consists of a 5 degrees wide strip along the Galactic meridian l = 254 degrees extending from the Galactic plane to the South Galactic pole. We identify three zones distinguished by polarized emission properties: the disc, the halo and a transition region connecting them. The halo section lies at latitudes vertical bar b vertical bar > 40 degrees and has weak and smooth polarized emission mostly at large scale with steep angular power spectra of median slope beta(med) similar to -2.6. The disc region covers the latitudes vertical bar b vertical bar

We present observations and CMB foreground analysis of the Parkes Galactic Meridian Survey (PGMS), an investigation of the Galactic latitude behaviour of the polarized synchrotron emission at 2.3 GHz with the Parkes Radio Telescope. The survey consists of a 5-deg wide strip along the Galactic meridian l=254-deg extending from Galactic plane to South Galactic pole. We identify three zones distinguished by polarized emission properties: the disc, the halo, and a transition region connecting them. The halo section lies at latitudes |b| > 40-deg and has weak and smooth polarized emission mostly at large scale with steep angular power spectra of median slope $\beta_{\rm med} \sim -2.6$. The disc region covers the latitudes |b, Comment: 23 pages, 22 Figures. Accepted for publication on MNRAS. Some figures have been reduced in resolution. Replaced with the accepted version, 3 figures, more details on instrument performances, and map of polarization spectral index added

We present results of polarization observations at 1.4 GHz of the two fields imaged by the DASI experiment (alpha = 23(h)30(m), delta = -55 degrees and alpha = 00(h)30(m), delta = -55 degrees, respectively). Data were taken with the Australia Telescope Compact Array with 3.4-arcmin resolution and similar to 0.18-mJy beam(-1) sensitivity. The emission is dominated by point sources, and we do not find evidence for diffuse synchrotron radiation even after source subtraction. This allows to estimate an upper limit of the diffuse polarized emission. The extrapolation to 30 GHz suggests that the synchrotron radiation is lower than the polarized signal measured by the DASI experiment by at least two orders of magnitude. This further supports the conclusions drawn by the DASI team itself about the negligible Galactic foreground contamination in their data set, improving by a factor of similar to 5 the upper limit estimated by Leitch et al. The dominant point-source emission allows us to estimate the contamination of the cosmic microwave background (CMB) by extragalactic foregrounds. We computed the power spectrum of their contribution, and its extrapolation to 30 GHz provides a framework where the CMB signal should dominate. However, our results do not match the conclusions of the DASI team about the negligibility of point-source contamination, suggesting taking into account a source subtraction from the DASI data.

We present results of polarization observations at 1.4 GHz of the two fields imaged by the DASI experiment ($\alpha = 23^{\rm h} 30^{\rm m}$, $\delta = -55^{\circ}$ and $\alpha = 00^{\rm h} 30^{\rm m}$, $\delta = -55^{\circ}$, respectively). Data were taken with the Australia Telescope Compact Array with 3.4 arcmin resolution and $\sim 0.18$ mJy beam$^{-1}$ sensitivity. The emission is dominated by point sources and we do not find evidence for diffuse synchrotron radiation even after source subtraction. This allows to estimate an upper limit of the diffuse polarized emission. The extrapolation to 30 GHz suggests that the synchrotron radiation is lower than the polarized signal measured by the DASI experiment by at least 2 orders of magnitude. This further supports the conclusions drawn by the DASI team itself about the negligible Galactic foreground contamination in their data set, improving by a factor $\sim 5$ the upper limit estimated by Leitch et al. (2005). The dominant point source emission allows us to estimate the contamination of the CMB by extragalactic foregrounds. We computed the power spectrum of their contribution and its extrapolation to 30 GHz provides a framework where the CMB signal should dominate. However, our results do not match the conclusions of the DASI team about the negligibility of point source contamination, suggesting to take into account a source subtraction from the DASI data., Comment: 7 pages, six figures, submitted to MNRAS

We analyse the temperature-polarization cross-correlation in the Galactic synchrotron template that we have recently developed, and between the template and CMB temperature maps derived from WMAP data. Since the polarized synchrotron template itself uses WMAP data, we can estimate residual synchrotron contamination in the CMB $C_\ell^{TE}$ angular spectrum. While $C_2^{TE}$ appears to be contamined by synchrotron, no evidence for contamination is found in the multipole range which is most relevant for the fit of the cosmological optical depth., Accepted for pubblication on MNRAS Letter

We build template maps for the polarized Galactic--synchrotron emission on large angular scales (FWHM =~7$^\circ$), in the 20-90 GHz microwave range, by using WMAP data. The method, presented in a recent work, requires a synchrotron total intensity survey and the {\it polarization horizon} to model the polarized intensity and a starlight polarization map to model polarization angles. The basic template is obtained directly at 23 GHz with about 94% sky--coverage by using the synchrotron map released by the WMAP team. Extrapolations to 32, 60 and 90 GHz are performed by computing a synchrotron spectral index map, which strongly reduces previous uncertainties in passing from low (1.4 GHz) to microwave frequencies. Differing from low frequency data, none of our templates presents relevant structures out of the Galactic Plane. Our map at 90 GHz suggests that the synchrotron emission at high Galactic latitudes is low enough to allow a robust detection of the $E$--mode component of the cosmological signal on large--scale, even in models with low--reionization ($��= 0.05$). Detection of the weaker $B$--mode on the largest scales ($\ell < 10$) might be jeopardized unless the value $��= 0.17$ found by WMAP is confirmed, and $T/S > 0.1$. For lower levels of the gravitational--wave background the $B$--mode seems to be accessible only at the $\ell \sim 100$ peak and in selected low--synchrotron emission areas., 13 pages, 14 figures, accepted for pubblications by MNRAS. For a version with full resolution color figures see http://sp0rt.bo.iasf.cnr.it:8080/Docs/Public/papers.php

The Parkes Galactic Meridian Survey (PGMS) is a 5 deg X 90 deg strip to map the polarized synchrotron emission along a Galactic meridian from the Galactic plane down to the south Galactic pole. The survey is carried out at the Parkes radio telescope at a frequency of 2.3 GHz with 30 adjacent 8-MHz bands which enable Faraday Rotation studies. The scientific goal is twofold: (1) To probe the Galactic magnetism off the Galactic plane of which little is known so far. PGMS gives an insight into the Galactic magnetic field in the thick disc, halo, and disc-halo transition; (2) To study the synchrotron emission as foreground noise of the CMB Polarization, especially for the weak B-Mode which carries the signature of the primordial gravitational wave background left by the Inflation. PGMS observations have been recently concluded. In this contribution we present the survey along with first results., Comment: 7 pages, 6 figures, to appear in the proceedings of the conference "Magnetic Fields in the Universe II", eds. A. Esquivel et al., Rev. Mex. Astron. Astrof. (SC)

We study the contamination of the B-mode of the Cosmic Microwave Background Polarization (CMBP) by Galactic synchrotron in the lowest emission regions of the sky. The 22.8-GHz polarization map of the 3-years WMAP data release is used to identify and analyse such regions. Two areas are selected with signal-to-noise ratio S/N0.3). Such regions allow $T/S \sim 10^{-3}$ to be measured directly which approximately corresponds to the limit imposed by using a sky coverage of 15%. This opens interesting perspectives to investigate the inflationary model space in lowest emission regions., 5 pages, 3 figures, accepted for publication in MNRAS Letters

The BaR-SPOrt experiment is designed to measure the E -mode power spectrum of the Cosmic Microwave Background Polarization (CMBP) in the multipole range 50 l < 1000. In the current configuration at 32 GHz it can explore up to l = 400. Recent low frequency observations of the target region show that the synchrotron emission should not contamine the CMBP already at 32 GHz. A 6-month observation of a 6° × 6° sky area during the polar night, in ideal environmental conditions, will allow the Italian-French collaboration to both measure the E –mode power spectrum with appropriate sensitivity and perform important tests of the anomalous dust emission. The BaR-SPOrt 32 GHz instrument, now under test and ready for operations by Spring 2005, is proposed for 1–2 years Winter operations at Dome C.

To measure extremely faint signals like Cosmic Microwave Background Polarization (a few percent of CMB anisotropy) it is necessary to use very high sensitivity radiometers. This means to adopt low noise cryogenic front-end and long integration times. This is the case of BaR-SPOrt (Balloon borne Radiometer for Sky Polarization Observations), an experiment designed to measure the CMB polarization at sub-degree angular scales. In the millimeter range, where coherent radiometers (polarimeters) are typically employed, usual mechanical coolers can represent a limit to the final sensitivity due to their base temperature instability. As a matter of fact, in correlation polarimeter, temperature fluctuations of the front-end devices, can both mimic a polarized signal and severely limit instrumental sensitivity. Here we discuss in detail the thermal design of the cryostat housing the instrument with particular attention to the closed loop cryocooler adopted, which is able to guarantee 6W at 77K with a stability better than 0.1 K over several hours.

The measure of the faint polarized signal of the Cosmic Microwave Background (few percent of the CMB Anisotropy) requires instruments with very low contamination from systematic effects, high stability and high sensitivity. The BaR-SPOrt experiment, in sharing with the SPOrt project on ISS, is based on analog correlation receivers with components custom designed to match all of these requirements. Here we present the architecture, the design analysis and the status of the realization of the 32 GHz receiver.

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., Comment: 12 pages, 10 figures, Astronomical Telescopes and Instrumentation (Polaimetry in Astronomy) Hawaii August 2002 SPIE Meeting

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., 9 pages, 5 figures, conference proceeding, to appear in "Polarimetry in Astronomy", SPIE Symposium on 'Astronomical Telescopes and Instrumentation', Waikoloa, August 22-28 2002

We study the signal in the Cosmic Microwave Background (CMB) polarization anisotropy resulting from patchy reionization. It is well known that the primordial polarization of the CMB is very sensitive to the details of reionization. Combining a semi-analytic model of galaxy formation, in which the optical depth to the reionization epoch is in the range 0.014 to 0.048, with a high resolution N-body simulation we find that reionization generates a peak with amplitude 0.05~0.15 \mu K at large angular scales. The position of this peak reveals the size of the horizon at reionization, whilst its amplitude is a measure of the optical depth to reionization. On small scales, ionized patches prior to full reionization create a second order polarization signal due to the coupling of the free electron density fluctuation with the quadrupole moment of the temperature anisotropy. Careful study reveals that the coupling generates the same power spectra for electric and magnetic modes, whose amplitudes of polarization anisotropies from this process are predicted to be ~10nK. The amplitude depends strongly on the total baryon density $\Omega_b$ and on the spatial correlations of the free electron density in the ionized regions, and weakly on the fraction of ionizing photons able to escape their source galaxy, $f_{esc}$. The first- and second-order signals are therefore sensitive to the details of how the reionization occurred. Detection of these signals will place important constraints on the reionization history of the Universe., Comment: Final version, accepted by ApJ

BaR-SPOrt is a project to measure the linearly polarised emission of 20degtimes20deg sky patches from a stratospheric balloon, at 32 GHz and 90 GHz. It consists of correlation polarimeters for direct measurements of the Q and U Stokes parameters, coupled to optics providing a beam of 0.5deg (32 GHz) and 0.2deg (90 GHz). The instrument design is described. Particular emphasis is put on the hardware solutions adopted to reduce the systematic effects in high sensitivity polarisation measurements

We describe the Planck HFI design and expected performances for measuring CMB polarisation., Comment: Proceedings of the Pol2001 "Astrophysical Polarised Backgrounds" conference, Bologna, 9-12 october 2001

SPOrt is a space experimental aimed at studying the polarization of the CMB and of the diffused Galactic Background in the microwave range (22-90 GHz). Here we present the project as well as its main scientific goals.

BaR-SPOrt is a balloon-borne experiment in the microwave range (32–90 GHz) aimed at studying the polarization of the CMB and of the diffused Galactic Background. Here we present the main scientific goals as well as the observing strategies of the project.