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Vinyaikin, E. N.; Paseka, A. M.; Teplykh, A. I.

doi:10.1023/a:1015993408092

Cited by 3 publications

(5 citation statements)

References 1 publication

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“…First, there is no overlap in ( u , v ) coverage between their single‐dish (or phased antenna array) measurements and our interferometer results (which have no zero‐length baselines). Secondly, one must interpolate between frequencies to compare to our 150 MHz results; Vinyaikin et al (1996) can fit physical models with polarization nulls between 88 and 200 MHz, but the number and location of such nulls are not uniquely determined. Finally, the observations are in different parts of the sky, and one would not expect geometry‐dependent properties such as the frequencies of polarization nulls to be exactly the same.…”

Section: Discussionmentioning

confidence: 99%

“…We see no reason to think our field would be different in this regard. Vinyaikin et al (1996) provide a model of diffuse Galactic polarization toward the North Celestial Pole (NCP). They find polarization p Q 2 + U 2 of 3.5 ± 1.0 K at 88 MHz (with a 24 • FWHM beam) and 2.15 ± 0.25 K at 200 MHz (8 • FWHM).…”

Section: Discussionmentioning

confidence: 99%

“…1 1 Note that the numbers in table 1 of Vinyaikin et al (1996) are actually due to their normalization convention for polarized brightness. …”

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confidence: 99%

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The GMRT EoR experiment: limits on polarized sky brightness at 150 MHz

Pen¹,

Chang²,

Hirata³

et al. 2009

Monthly Notices of the Royal Astronomical Society

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The Giant Metrewave Radio Telescope (GMRT) reionization effort aims to map out the large‐scale structure of the Universe during the epoch of reionization (EoR). Removal of polarized Galactic emission is a difficult part of any 21 cm EoR programme, and we present new upper limits to diffuse polarized foregrounds at 150 MHz. We find no high‐significance evidence of polarized emission in our observed field at mid‐galactic latitude (J2000 08h26m+26). We find an upper limit on the two‐dimensional angular power spectrum of diffuse polarized foregrounds of (l2Cl/2π)1/2 < 3 K in frequency bins of width δν= 1 MHz at 300 < l < 1000. The three‐dimensional power spectrum of polarized emission, which is most directly relevant to EoR observations, is [k3PP(k)/2π2]1/2 < 2 K at k⊥ > 0.03 h Mpc−1, k < 0.1 h Mpc−1. This can be compared to the expected EoR signal in total intensity of [k3P(k)/2π2]1/2∼ 10 mK. We find that polarized structure is substantially weaker than suggested by extrapolation from higher frequency observations, so the new low upper limits reported here reduce the anticipated impact of these foregrounds on EoR experiments. We discuss the Faraday beam and depth depolarization models and compare predictions of these models to our data. We report on a new technique for polarization calibration using pulsars, as well as a new technique to remove broad‐band radio frequency interference. Our data indicate that, on the edges of the main beam at the GMRT, polarization squint creates ∼3 per cent leakage of unpolarized power into polarized maps at zero rotation measure. Ionospheric rotation was largely stable during these solar minimum nighttime observations.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

See 1 more Smart Citation

The GMRT EoR experiment: limits on polarized sky brightness at 150 MHz

Pen¹,

Chang²,

Hirata³

et al. 2009

Monthly Notices of the Royal Astronomical Society

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“…The global 21 cm experiments to date have been single element, making it difficult to make a precise comparison with interferometric galaxy polarization surveys conducted at similar frequencies (Pen et al 2009;Bernardi et al 2013). Vinyaikin et al (1996) measured 3.5 ± 1.0 K at 88 MHz (24 • FWHM, phased array) and 2.15 ± 0.25 K at 200 MHz (8 • FWHM, single dish) for the value of Q 2 + U 2 toward the north celestial pole.…”

Section: Susceptibility To Faraday Rotationmentioning

confidence: 97%

ERASING THE VARIABLE: EMPIRICAL FOREGROUND DISCOVERY FOR GLOBAL 21 cm SPECTRUM EXPERIMENTS

Switzer¹,

Liu²

2014

ApJ

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Spectral measurements of the 21 cm monopole background have the promise of revealing the bulk energetic properties and ionization state of our universe from z ∼ 6 − 30. Synchrotron foregrounds are orders of magnitude larger than the cosmological signal, and are the principal challenge faced by these experiments. While synchrotron radiation is thought to be spectrally smooth and described by relatively few degrees of freedom, the instrumental response to bright foregrounds may be much more complex. To deal with such complexities, we develop an approach that discovers contaminated spectral modes using spatial fluctuations of the measured data. This approach exploits the fact that foregrounds vary across the sky while the signal does not. The discovered modes are projected out of each line of sight of a data cube. An angular weighting then optimizes the cosmological signal amplitude estimate by giving preference to lower-noise regions. Using this method, we show that it is essential for the passband to be stable to at least ∼ 10 −4 . In contrast, the constraints on the spectral smoothness of the absolute calibration are mainly aesthetic if one is able to take advantage of spatial information. To the extent it is understood, controlling polarization to intensity leakage at the ∼ 10 −2 level will also be essential to rejecting Faraday rotation of the polarized synchrotron emission.

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“…By now the linearly polarized component of the Galactic diffuse synchrotron radio emission has been partly investigated at frequencies of meter (e.g. [1]) and decimeter (e.g. [2,3]) wavebands up to 2.695 GHz [4].…”

Section: Introductionmentioning

confidence: 99%

Observations of linear polarization of background galactic radio emission in selected directions at 8.3 GHz

Vinyajkin¹,

Carretti²,

Cortiglioni³

et al. 2002

AIP Conference Proceedings

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Polarization observations of the Galactic radio emission at 8.3 GHz were made by the 32-m Medicina (Italy) radio telescope in four pixels (HPBW=4.'8). A method of tracking around the upper culmination was used in order to use the rotation of the parallactic angle for detecting the weak linearly polarized Galactic radio emission against the background of relatively strong and variable spurious and instrumental polarization. The well known source 3C 286 was used as calibrator. As a result the brightness temperatures of linearly polarized component of the Galactic radio emission and positions angles were measured for all pixels. Comparison was made for the pixels in the first Galactic quadrant with Duncan et al. 2695 MHz polarization measurements and as a result spectral indexes and rotation measures were determined.

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Cited by 3 publications

References 1 publication

The GMRT EoR experiment: limits on polarized sky brightness at 150 MHz

The GMRT EoR experiment: limits on polarized sky brightness at 150 MHz

ERASING THE VARIABLE: EMPIRICAL FOREGROUND DISCOVERY FOR GLOBAL 21 cm SPECTRUM EXPERIMENTS

Observations of linear polarization of background galactic radio emission in selected directions at 8.3 GHz

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