1.4-GHz polarimetric observations of the two fields imaged by the DASI experiment

Bernardi, G.; Carretti, E.; Sault, R. J.; Cortiglioni, S.; Poppi, S.

doi:10.1111/j.1365-2966.2006.10649.x

Cited by 11 publications

(9 citation statements)

References 34 publications

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“…The case of a slope α=−3.5 is also reported for the S/N < 2 region (yellow shaded). For comparison, the plot shows CMB spectra for three different values of r = T / S , the synchrotron emission detected in the two low emission areas in the target fields of the BOOMERanG ( C B BOOM , Carretti et al 2005b) and BaR‐SPOrt experiments ( C B BaR , Carretti et al 2006), and the upper limit found in the DASI fields ( C B DASI , Bernardi et al 2006). Finally, the general contamination at high Galactic latitude, as estimated by the WMAP team using 74.3 per cent of the sky, is also reported: the spectrum at 22.8 GHz is considered (Page et al 2006) and extrapolated to 70 GHz.…”

Section: Implication For Cmbp B‐mode and Discussionmentioning

confidence: 99%

B-mode contamination by synchrotron emission from 3-yr Wilkinson Microwave Anisotropy Probe data

Carretti

Bernardi

Cortiglioni

2006

Monthly Notices of the Royal Astronomical Society: Letters

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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‐yr Wilkinson Microwave Anisotropy Probe (WMAP) data release is used to identify and analyse such regions. Two areas are selected with signal‐to‐noise ratio S/N < 2 and S/N < 3, covering ∼16 and ∼26 per cent fraction of the sky, respectively. The polarization power spectra of these two areas are dominated by the sky signal on large angular scales (multipoles ℓ < 15), while the noise prevails on degree scales. Angular extrapolations show that the synchrotron emission competes with the CMBP B‐mode signal for tensor‐to‐scalar perturbation power ratio T/S= 10−3–10−2 at 70 GHz in the 16 per cent lowest emission sky (S/N < 2 area). These values worsen by a factor ∼5 in the S/N < 3 region. The novelty is that our estimates regard the whole lowest emission regions and outline a contamination better than that of the whole high Galactic latitude sky found by the WMAP team (T/S > 0.3). Such regions allow T/S∼ 10−3 to be measured directly which approximately corresponds to the limit imposed by using a sky coverage of 15 per cent. This opens interesting perspectives on the investigation of the inflationary model space in lowest emission regions.

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Section: Implication For Cmbp B‐mode and Discussionmentioning

confidence: 99%

B-mode contamination by synchrotron emission from 3-yr Wilkinson Microwave Anisotropy Probe data

Carretti

Bernardi

Cortiglioni

2006

Monthly Notices of the Royal Astronomical Society: Letters

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“… C B WMAP is the general contamination at high Galactic latitude, as estimated by the WMAP team using an ∼75 per cent sky fraction at 22.8 GHz (Page et al 2007). Spectra measured in small areas selected for their low emission are also shown: the target fields of the experiments BOOMERanG ( C B BOOM , Carretti et al 2005b) and BaR‐SPOrt ( C B BaR ; Carretti et al 2006a) and the upper limit found in the two fields of the experiment DASI ( C B DASI ; Bernardi et al 2006). Finally, C S/N<2 shows the estimate of the emission in the best 15 per cent of the sky (Carretti et al 2006b; the shaded area indicates the uncertainties), while C DRAO the values found in some intermediate regions using 1.4‐GHz data (La Porta et al 2006).…”

Section: Introductionmentioning

confidence: 99%

The Parkes Galactic Meridian Survey: observations and CMB polarization foreground analysis

Carretti

Haverkorn

McConnell

et al. 2010

Monthly Notices of the Royal Astronomical Society

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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 • wide strip along the Galactic meridian l = 254 • 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 |b| > 40 • and has weak and smooth polarized emission mostly at large scale with steep angular power spectra of median slope β med ∼ −2.6. The disc region covers the latitudes |b| < 20 • and has a brighter, more complex emission dominated by the small scales with flatter spectra of median slope β med = −1.8. The transition region has steep spectra as in the halo, but the emission increases towards the Galactic plane from halo to disc levels. The change of slope and emission structure at b ∼ −20 • is sudden, indicating a sharp disc-halo transition. The whole halo section is just one environment extended over 50 • with very low emission which, once scaled to 70 GHz, is equivalent to the CMB B-mode emission for a tensor-toscalar perturbation power ratio r halo = (3.3 ± 0.4) × 10 −3 . Applying a conservative cleaning procedure, we estimate an r detection limit of δr ∼ 2 × 10 −3 at 70 GHz (3σ confidence limit) and, assuming a dust polarization fraction of <12 per cent, δr ∼ 1 × 10 −2 at 150 GHz. The 150-GHz limit matches the goals of planned sub-orbital experiments, which can therefore be conducted at this high frequency. The 70-GHz limit is close to the goal of proposed next-generation space missions, which thus might not strictly require space-based platforms.

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“…A full-sky absolutely-calibrated polarization map at 1.4 GHz with 0.5 • resolution was recently published by Wolleben et al (2006). Selected regions of low total intensity synchrotron emission have been observed between 1.4 and 2.3 GHz (Bernardi et al 2003;Carretti et al 2005a;Carretti et al 2005b;Carretti et al 2006;Bernardi et al 2006) characterizing the spatial properties of the diffuse polarized emission down to arcmin scales with the purpose of studying the contamination of the cosmic microwave background polarization.…”

Section: Introductionmentioning

confidence: 99%

Foregrounds for observations of the cosmological 21 cm line

Bernardi¹,

Bruyn

Brentjens

et al. 2009

A&A

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230

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Context. The cosmological 21 cm line promises to be a formidable tool for cosmology, allowing the investigation of the end of the so-called dark ages, when the first galaxies formed. Aims. Astrophysical foregrounds are expected to be about three orders of magnitude greater than the cosmological signal and therefore represent a serious contamination of the cosmological 21 cm line. Detailed knowledge of both their intensity and polarization structure on the relevant angular scale of 1-30 arcmin will be essential for extracting the cosmological signal from the data. Methods. We present the first results from a series of observations conducted with the Westerbork telescope in the 140-160 MHz range with a 2 arcmin resolution aimed at characterizing the properties of the foregrounds for epoch of reionization experiments. The polarization data were analysed through the rotation measure synthesis technique. We computed total intensity and polarization angular power spectra. Results. For the first time we have detected fluctuations in the Galactic diffuse emission on scales greater than 13 arcmin at 150 MHz, in the low Galactic latitude area known as Fan region, centred at α = 3 h 10 m , δ = 65 • 30 . Those fluctuations have an rms of 14 K. The total intensity power spectrum shows a power-law behaviour down to ∼900 with slope β I = −2.2 ± 0.3. The detection of diffuse emission at smaller angular scales is limited by residual point sources. We measured an rms confusion noise of ∼3 mJy beam −1 . Diffuse polarized emission was also detected for the first time at this frequency. The polarized signal shows complex structure both spatially and along the line of sight. The polarization power spectrum is not affected by residual point sources and is only limited by the thermal noise. It shows a power-law behaviour down to ∼2700 with slope β P = −1.65±0.15. The rms of polarization fluctuations is 7.2 K on 4 arcmin scales. Conclusions. The measured total intensity fluctuations are used to estimate the foreground contamination on the cosmological signal.By extrapolating the spectrum of total intensity emission, we find a contamination of δT = ( + 1)C I /2π ∼ 5.7 K on 5 arcmin scales and a corresponding rms value of ∼18.3 K at the same angular scale. The level of the polarization power spectrum is δT ∼ 3.3 K on 5 arcmin scales. However, the Fan region cannot be taken as representative of other sky regions, given its exceptionally bright polarized signal, but is likely to represent an upper limit on the sky brightness at moderate and high Galactic latitude.

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1.4-GHz polarimetric observations of the two fields imaged by the DASI experiment

Cited by 11 publications

References 34 publications

B-mode contamination by synchrotron emission from 3-yr Wilkinson Microwave Anisotropy Probe data

B-mode contamination by synchrotron emission from 3-yr Wilkinson Microwave Anisotropy Probe data

The Parkes Galactic Meridian Survey: observations and CMB polarization foreground analysis

Foregrounds for observations of the cosmological 21 cm line

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