A Linear Polarization Survey of the Southern Sky at 408 MC/S

Mathewson, DS; Milne, D. K.

doi:10.1071/ph650635

Cited by 47 publications

(38 citation statements)

References 11 publications

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“…A general and remarkable result (see Sect. 5) is that (Brouw & Spoelstra 1976) and of the Parkes southern sky survey (Mathewson & Milne 1965). Unfortunately, the vector length has a different scale in the two original figures, therefore only a direct comparison of the direction is feasible.…”

Section: Discussionmentioning

confidence: 99%

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A multifrequency angular power spectrum analysis of the Leiden polarization surveys

Porta

Burigana

2006

A&A

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The Galactic synchrotron emission is expected to be the most relevant source of astrophysical contamination in cosmic microwave background polarization measurements, at least at frequencies ν < ∼ 70 GHz and at angular scales θ > ∼ 30 . We present a multifrequency analysis of the Leiden surveys, linear polarization surveys covering the Northern Celestial Hemisphere at five frequencies between 408 MHz and 1411 MHz. By implementing specific interpolation methods to deal with these irregularly sampled data, we produced maps of the polarized diffuse Galactic radio emission with a pixel size 0.92 • . We derived the angular power spectrum (APS) (PI, E, and B modes) of the synchrotron dominated radio emission as function of the multipole, . We considered the whole covered region and some patches at different Galactic latitudes. By fitting the APS in terms of power laws (C ∼ κ · α ), we found spectral indices that steepen with increasing frequency: from α ∼ −(1−1.5) at 408 MHz to α ∼ −(2−3) at 1411 MHz for 10 < ∼ < ∼ 100 and from α ∼ −0.7 to α ∼ −1.5 for lower multipoles (the exact values depending on the considered sky region and polarization mode). The bulk of this flattening at lower frequencies can be interpreted in terms of Faraday depolarization effects. We then considered the APS at various fixed multipoles and its frequency dependence. Using the APSs of the Leiden surveys at 820 MHz and 1411 MHz, we determined possible ranges for the rotation measure, RM, in the simple case of an interstellar medium slab model. Also taking into account the polarization degree at 1.4 GHz, it is possible to break the degeneracy between the identified RM intervals. The most reasonable of them turned out to be RM ∼ 9−17 rad/m 2 although, given the uncertainty on the measured polarization degree, RM values in the interval ∼53−59 rad/m 2 cannot be excluded.

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Section: Discussionmentioning

confidence: 99%

“…A linear polarization survey of the Southern sky had previously been carried out at 408 MHz using the Parkes telescope (Mathewson & Milne 1965); unfortunately these data have never been put in digital form. In Fig.…”

Section: Discussionmentioning

confidence: 99%

A multifrequency angular power spectrum analysis of the Leiden polarization surveys

Porta

Burigana

2006

A&A

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“…However, only a limited number of short-baselines are available in this mode and sensitivity is compromised to provide them. Single dish polarimetric observations at long wavelengths provide access to large-scale structure but so far there has only been one such observation (Mathewson & Milne 1965) and it suffered from poor sensitivity and spatial sampling. Furthermore, single dish observations below 300 MHz also lack resolution.…”

Section: Introductionmentioning

confidence: 99%

Low-Frequency Observations of Linearly Polarized Structures in the Interstellar Medium Near the South Galactic Pole

Lenc

Gaensler

Sun

et al. 2016

ApJ

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We present deep polarimetric observations at 154 MHz with the Murchison Widefield Array (MWA), covering 625 deg 2 centered on α=0 h andδ=−27°. The sensitivity available in our deep observations allows an in-band, frequency-dependent analysis of polarized structure for the first time at long wavelengths. Our analysis suggests that the polarized structures are dominated by intrinsic emission but may also have a foreground Faraday screen component. At these wavelengths, the compactness of the MWA baseline distribution provides excellent snapshot sensitivity to large-scale structure. The observations are sensitive to diffuse polarized emission at ∼54′ resolution with a sensitivity of 5.9 mJy beam −1 and compact polarized sources at ∼2 4 resolution with a sensitivity of 2.3 mJy beam −1 for a subset (400 deg 2 ) of this field. The sensitivity allows the effect of ionospheric Faraday rotation to be spatially and temporally measured directly from the diffuse polarized background. Our observations reveal large-scale structures (∼1°-8°in extent) in linear polarization clearly detectable in ∼2 minute snapshots, which would remain undetectable by interferometers with minimum baseline lengths of >110 m at 154 MHz. The brightness temperature of these structures is on average 4 K in polarized intensity, peaking at 11 K. Rotation measure synthesis reveals that the structures have Faraday depths ranging from −2 to 10 rad m −2 with a large fraction peaking at approximately+1 rad m −2 . We estimate a distance of 51±20 pc to the polarized emission based on measurements of the in-field pulsar J2330-2005. We detect four extragalactic linearly polarized point sources within the field in our compact source survey. Based on the known polarized source population at 1.4 GHz and non-detections at 154 MHz, we estimate an upper limit on the depolarization ratio of 0.08 from 1.4 GHz to 154 MHz.

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“…The polarization of the diffuse radio emission that was finally discovered in 1962 had a long period of quiescence after the surveys of Wielebinski & Shakeshaft (1964), Mathewson & Milne (1965) and Brouw & Spoelstra (1976) have been published. The follow-up investigation by Spoelstra (1984) concluded that the Rotation Measure (RM) in the ISM towards l = 140…”

Section: Radio Continuum Polarizationmentioning

confidence: 99%

What do we really know about the magnetic fields of the Milky Way?

Wielebinski

2008

Proc. IAU

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Abstract.We have several methods of measuring magnetic fields in the Milky Way. We can study optical polarization, radio polarization, rotation measures of pulsars and extragalactic radio sources as well as include Zeeman results. Each of the above mentioned methods was at times used to make a model of the magnetic fields of the Milky Way. However one or two of the data sets by themselves cannot tell us the whole story. Any model of the magnetic fields must be able to fit all the observational results. At the present time a lot of progress has been made. We have increased our data bases in most of the observational areas. However a robust model of the magnetic field of the Milky Way has not yet emerged. We must possibly wait to the era of SKA.

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A Linear Polarization Survey of the Southern Sky at 408 MC/S

Cited by 47 publications

References 11 publications

A multifrequency angular power spectrum analysis of the Leiden polarization surveys

A multifrequency angular power spectrum analysis of the Leiden polarization surveys

Low-Frequency Observations of Linearly Polarized Structures in the Interstellar Medium Near the South Galactic Pole

What do we really know about the magnetic fields of the Milky Way?

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