High Galactic latitude polarized emission at 1.4 GHz and implications for cosmic microwave background observations

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

doi:10.1111/j.1365-2966.2005.08761.x

Cited by 43 publications

(30 citation statements)

References 26 publications

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“…The distribution of the fluctuations in the polarization angle are obtained from the observations in the radio band at low and medium galactic latitudes. These measures give a rather high fluctuation level reflecting the small scale structure of the galactic magnetic field (Uyaniker et al 1999;Duncan et al 1999), scaling as −2 from sub-degree to arcminute scales (Tucci et al 2002), and consistent with recent observations at medium galactic latitudes (Carretti et al 2005). The template for the polarization angle was obtained by adopting the form above for the angular power spectrum, and assuming a Gaussian distribution.…”

Section: Diffuse Galactic Emissionsupporting

confidence: 79%

Making maps from Planck LFI 30 GHz data

Ashdown

Baccigalupi

Balbi

et al. 2007

A&A

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This paper is one of a series describing the performance and accuracy of map-making codes as assessed by the Planck CTP working group. We compare the performance of multiple codes written by different groups for making polarized maps from Planck-sized, all-sky cosmic microwave background (CMB) data. Three of the codes are based on a destriping algorithm, whereas the other three are implementations of a maximum-likelihood algorithm. Previous papers in the series described simulations at 100 GHz (Poutanen et al. 2006(Poutanen et al. , A&A, 449, 1311 and 217 GHz (Ashdown et al. 2007, A&A, 467, 761). In this paper we make maps (temperature and polarisation) from the simulated one-year observations of four 30 GHz detectors of Planck Low Frequency Instrument (LFI). We used Planck Level S simulation pipeline to produce the observed time-ordered-data streams (TOD). Our previous studies considered polarisation observations for the CMB only. For this paper we increased the realism of the simulations and included polarized galactic foregrounds in our sky model, which is based on the version 0.1 of the Planck reference sky. Our simulated TODs comprised dipole, CMB, diffuse galactic emissions, extragalactic radio sources, and detector noise. The strong subpixel signal gradients arising from the foreground signals couple to the output map through the map-making and cause an error (signal error) in the maps. Destriping codes have smaller signal error than the maximum-likelihood codes. We examined a number of schemes to reduce this error. On the other hand, the maximum-likelihood map-making codes can produce maps with lower residual noise than destriping codes.

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Section: Diffuse Galactic Emissionsupporting

confidence: 79%

Making maps from Planck LFI 30 GHz data

Ashdown

Baccigalupi

Balbi

et al. 2007

A&A

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“…However, this comparison could not be reliable because of Faraday rotation effects. Carretti et al (2005a) find that a power transfer from large to small angular scales occurs, as the Faraday rotation is strongly modifying the emission pattern. This results both in a steeper slope and power enhancement of the power spectrum on subdegree scales.…”

Section: Power Spectrum Analysismentioning

confidence: 79%

“…The diffuse synchrotron emission of the Galaxy is considered to be one of the most relevant polarization contaminant and is expected to dominate the foreground contribution at frequencies less than 100 GHz. Recent measurements performed in a low‐emission area at both 1.4 and 2.3 GHz indicate that the synchrotron signal does not represent an obstacle for the E mode at high Galactic latitude and at frequencies higher than 30 GHz (Bernardi et al 2003; Carretti et al 2005a,b). However, this is just one sample that may not be representative of the situation throughout high Galactic latitudes, and other measurements in different areas are required to confirm this first evaluation.…”

Section: Introductionmentioning

confidence: 99%

“…In this paper, we present deep 1.4‐GHz observations of an area in the northern field. Centred at RA = 10 h 58 m , Dec. =+42°18′ (B1950), the observed area features very high Galactic latitudes ( l ∼ 172°, b ∼+63°), which should prevent the significant alterations of the polarized emission by Faraday rotation possible at this frequency for | b | < 40°–50° (Carretti et al 2005a). This leads to estimates of the E ‐ and B ‐mode power spectra which can safely be extrapolated to the frequency range relevant for CMB studies.…”

Section: Introductionmentioning

confidence: 99%

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Deep 1.4-GHz observations of diffuse polarized emission

Carretti

Poppi

Reich

et al. 2006

Monthly Notices of the Royal Astronomical Society

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Polarized diffuse emission observations at 1.4-GHz in a high Galactic latitude area of the northern Celestial hemisphere are presented. The 3.2 X 3.2 deg^2 field, centred at RA = 10h 58m, Dec = +42deg 18' (B1950), has Galactic coordinates l~172deg, b~+63deg and is located in the region selected as northern target of the BaR-SPOrt experiment. Observations have been performed with the Effelsberg 100-m telescope. We find that the angular power spectra of the E- and B-modes have slopes of beta_E = -1.79 +/- 0.13 and beta_B = -1.74 +/- 0.12, respectively. Because of the very high Galactic latitude and the smooth emission, a weak Faraday rotation action is expected, which allows both a fair extrapolation to Cosmic Microwave Background Polarization (CMBP) frequencies and an estimate of the contamination by Galactic synchrotron emission. We extrapolate the E-mode spectrum up to 32-GHz and confirm the possibility to safely detect the CMBP E-mode signal in the Ka band found in another low emission region (Carretti et al. 2005b). Extrapolated up to 90-GHz, the Galactic synchrotron B-mode looks to compete with the cosmic signal only for models with a tensor-to-scalar perturbation power ratio T/S < 0.001, which is even lower than the T/S value of 0.01 found to be accessible in the only other high Galactic latitude area investigated to date. This suggests that values as low as T/S = 0.01 might be accessed at high Galactic latitudes. Such low emission values can allow a significant red-shift of the best frequency to detect the CMBP B-mode, also reducing the contamination by Galactic dust, and opening interesting perspectives to investigate Inflation models.Comment: 8 pages, 8 figures, accepted for publication in MNRA

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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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198

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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High Galactic latitude polarized emission at 1.4 GHz and implications for cosmic microwave background observations

Cited by 43 publications

References 26 publications

Making maps from Planck LFI 30 GHz data

Making maps from Planck LFI 30 GHz data

Deep 1.4-GHz observations of diffuse polarized emission

Foregrounds for observations of the cosmological 21 cm line

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