An Upper Limit on the Linear Polarization Fraction of the GW170817 Radio Continuum

Abstract 3FGL J1544.6−1125 is a candidate transitional millisecond pulsar (tMSP). Similar to the well-established tMSPs—PSR J1023+0038, IGR J18245−2452, and XSS J12270−4859—3FGL J1544.6−1125 shows γ-ray emission and discrete X-ray “low” and “high” modes during its low-luminosity accretion-disk state. Coordinated radio/X-ray observations of PSR J1023+0038 in its current low-luminosity accretion-disk state showed rapidly variable radio continuum emission—possibly originating from a compact, self-absorbed jet, the “propellering” of accretion material, and/or pulsar moding. 3FGL J1544.6−1125 is currently the only other (candidate) tMSP system in this state, and can be studied to see whether tMSPs are typically radio-loud compared to other neutron star binaries. In this work, we present a quasi-simultaneous Very Large Array and Swift radio/X-ray campaign on 3FGL J1544.6−1125. We detect 10 GHz radio emission varying in flux density from 47.7 ± 6.0 μJy down to ≲15 μJy (3σ upper limit) at four epochs spanning three weeks. At the brightest epoch, the radio luminosity is L 5 GHz = (2.17 ± 0.17) × 1027 erg s−1 for a quasi-simultaneous X-ray luminosity L 2–10 keV = (4.32 ± 0.23) × 1033 erg s−1 (for an assumed distance of 3.8 kpc). These luminosities are close to those of PSR J1023+0038, and the results strengthen the case that 3FGL J1544.6−1125 is a tMSP showing similar phenomenology to PSR J1023+0038.

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Seeking for magnetic fields in rotating disk/jets with ALMA polarimetry

Proceedings of the International Astronomical Union ◽

10.1017/s1743921319003806 ◽

2018 ◽

Vol 14 (A30) ◽

pp. 128-129

Author(s):

Francesca Bacciotti ◽

Josep Miquel Girart ◽

Marco Padovani

Keyword(s):

Linear Polarization ◽

Thermal Emission ◽

Rotating Disk ◽

Polarization Angle ◽

T Tauri ◽

Magnetic Signatures ◽

Dust Evolution ◽

First Time ◽

Crucial Ingredient ◽

Polarization Fraction

AbstractThe Atacama Large Millimeter/submillimeter Array (ALMA) is providing important advances in studies of star formation. In particular, polarimetry can reveal the disk magnetic configuration, a crucial ingredient in many processes, as, for example, the transport of angular momentum. We analized ALMA Band 7 (870 μm) polarimetric data at 0.”2 resolution for the young rotating disk/jet systems DG Tau and CW Tau, to find magnetic signatures. From the Stokes I, U, Q maps, we derive the linear polarization intensity, $P = \sqrt {{Q^2} + {U^2}} $ , the linear polarization fraction, and the polarization angle. The alignment of the latter with the disk minor axis (Fig. 1) shows that self-scattering of dust thermal emission rather than magnetic alignment dominates the polarization in both targets (Bacciotti et al. 2018). However, several dust properties can be diagnosed comparing the polarization data with the models of self-scattering (e.g. Kataoke et al. 2017, Yang et al. 2017). The maximum grain size turns out to be in the range 50 - 70 μm for DG Tau and 100 - 150 μm for CW Tau. The asymmetry of the polarized intensity in DG Tau, observed for the first time around a T Tauri star, indicates that the disk is flared. Moreover, the observed belt-like feature may betray the presence of a disk substructure. In contrast, the polarization maps of CW Tau indicate that here the grains have settled to the disk midplane. Polarimetry is thus very important in studies of the dust evolution.

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The Local Magnetic Field in the Milky Way

International Astronomical Union Colloquium ◽

10.1017/s0252921100071049 ◽

1997 ◽

Vol 166 ◽

pp. 239-242

Author(s):

B. Uyaniker ◽

E. Fürst ◽

W. Reich ◽

P. Reich ◽

R. Wielebinski

Keyword(s):

Magnetic Field ◽

Linear Polarization ◽

Milky Way ◽

Radio Continuum ◽

Local Magnetic Field ◽

Center Frequency ◽

Total Power ◽

Max Planck

AbstractA radio continuum survey at medium Galactic latitudes with the 100−m telescope of the Max-Planck-Institut für Radioastronomie is being carried out at a center frequency of 1.4 GHz in total power and linear polarization. We present polarization and depolarization structures detected at medium latititudes with no corresponding observable structure in total power emission. Existence of such kind of polarization structures imply that the emission, due to the Faraday modulation of the Galactic synchrotron foreground, occurs in thin sheetlike regions. This phenomenon is a sign for fluctuating local magnetic field.

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Radio Continuum Surveys of the Galaxy and Galaxies

Symposium - International Astronomical Union ◽

10.1017/s0074180900169074 ◽

2002 ◽

Vol 199 ◽

pp. 262-267

Author(s):

Richard Wielebinski

Keyword(s):

Magnetic Fields ◽

Radio Emission ◽

Linear Polarization ◽

Angular Resolution ◽

Low Frequency ◽

Radio Continuum ◽

Sky Surveys ◽

The Galaxy ◽

Nearby Galaxies ◽

Radio Frequencies

Radio sky surveys give us basic information about the origin of the radio emission from the Galaxy. By mapping the sky at several radio frequencies a separation of the thermal and non-thermal emission components is possible. The major part of the low-frequency radio emission comes from the synchrotron process, the braking of relativistic electrons in magnetic fields. By mapping the linear polarization at several frequencies (required for the correction of the Faraday rotation) the orientation of the magnetic fields in the emitting regions can be deduced. Older all-sky surveys at 30, 150 and 408 MHz have now been supplemented by new observations of the Galaxy at 45 and 1420 MHz. These surveys, in addition to being important as tracers of the morphology of the magnetic fields in the Galaxy, are also required to correct for the ‘foreground’ features in cosmological studies of the COBE data and the PLANCK surveys in the future. Studies of the Galaxy in polarization have been made some years ago indicating high percentage of linear polarization in various directions. More recent work with good angular resolution has shown spectacular polarized intensity structures in selected regions. Low-frequency data with good angular resolution are urgently required for the interpretation of these features.Observations of nearby galaxies in radio continuum (both total power and polarized intensity) have given us the possibility to study magnetic fields in objects at known distances. Polarization observations of nearby galaxies have confirmed the existence of regular magnetic fields in practically every object so far studied. Originally data were obtained from large single-dish telescopes, notably from Effelsberg and Parkes. These data were greatly enhanced by the addition of higher resolution components from the VLA and ATCA respectively. These results indicate surprisingly homogeneous magnetic fields in most galaxies. High angular resolution observations with the GMRT at lower radio frequencies will add a new dimension to the data on galaxies.

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Discovery of Molecular-line Polarization in the Disk of TW Hya

The Astrophysical Journal ◽

10.3847/1538-4357/ac2503 ◽

2021 ◽

Vol 922 (2) ◽

pp. 139

Author(s):

Richard Teague ◽

Charles L. H. Hull ◽

Stéphane Guilloteau ◽

Edwin A. Bergin ◽

Anne Dutrey ◽

...

Keyword(s):

Linear Polarization ◽

Line Emission ◽

Emission Lines ◽

Continuum Emission ◽

Azimuthal Dependence ◽

Molecular Line ◽

Polarization Fraction ◽

Co Emission ◽

Higher Sensitivity ◽

The Continuum

Abstract We report observations of polarized line and continuum emission from the disk of TW Hya using the Atacama Large Millimeter/submillimeter Array. We target three emission lines, 12CO (3–2), 13CO (3–2), and CS (7–6), to search for linear polarization due to the Goldreich–Kylafis effect, while simultaneously tracing the continuum polarization morphology at 332 GHz (900 μm), achieving a spatial resolution of 0.″5 (30 au). We detect linear polarization in the dust continuum emission; the polarization position angles show an azimuthal morphology, and the median polarization fraction is ∼0.2%, comparable to previous, lower frequency observations. Adopting a “shift-and-stack” technique to boost the sensitivity of the data, combined with a linear combination of the Q and U components to account for their azimuthal dependence, we detect weak linear polarization of 12CO and 13CO line emission at a ∼10σ and ∼5σ significance, respectively. The polarization was detected in the line wings, reaching a peak polarization fraction of ∼5% and ∼3% for the two molecules between disk radii of 0.″5 and 1″. The sign of the polarization was found to flip from the blueshifted side of the emission to the redshifted side, suggesting a complex, asymmetric polarization morphology. Polarization is not robustly detected for the CS emission; however, a tentative signal, comparable in morphology to that found for the 12CO and 13CO emission, is found at a ≲3σ significance. We are able to reconstruct a polarization morphology, consistent with the azimuthally averaged profiles, under the assumption that this is also azimuthally symmetric, which can be compared with future higher-sensitivity observations.

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4.1. Radio continuum and molecular gas in the Galactic center: large-scale structures

Symposium - International Astronomical Union ◽

10.1017/s0074180900084473 ◽

1998 ◽

Vol 184 ◽

pp. 161-168

Author(s):

Yoshiaki Sofue

Keyword(s):

Radio Emission ◽

Linear Polarization ◽

Large Scale ◽

Galactic Center ◽

Thermal Emission ◽

Radio Continuum ◽

Molecular Gas ◽

Large Scale Structures ◽

Almost Everywhere ◽

Scale Structures

The radio emission from the Galactic Center is a mixture of thermal (free-free) and non-thermal (synchrotron) emissions (Fig. 1a). However, the spectral index in the central 3° region is flat almost everywhere (Sofue 1985), even in regions where strong linear polarization is detected. Therefore, a flat spectrum observed near the galactic center can no longer be taken as an indicator of thermal emission.

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Fractional polarization of extragalactic sources in the 500 deg2 SPTpol survey

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/stz2905 ◽

2019 ◽

Vol 490 (4) ◽

pp. 5712-5721 ◽

Cited By ~ 7

Author(s):

N Gupta ◽

C L Reichardt ◽

P A R Ade ◽

A J Anderson ◽

M Archipley ◽

...

Keyword(s):

Active Galactic Nuclei ◽

Power Spectra ◽

Galactic Nuclei ◽

Weighted Mean ◽

Full Sample ◽

The Real ◽

Upper Limit ◽

Upper Limits ◽

The Mean ◽

Polarization Fraction

ABSTRACT We study the polarization properties of extragalactic sources at 95 and 150 GHz in the SPTpol 500 deg2 survey. We estimate the polarized power by stacking maps at known source positions, and correct for noise bias by subtracting the mean polarized power at random positions in the maps. We show that the method is unbiased using a set of simulated maps with similar noise properties to the real SPTpol maps. We find a flux-weighted mean-squared polarization fraction 〈p2〉 = [8.9 ± 1.1] × 10−4 at 95 GHz and [6.9 ± 1.1] × 10−4 at 150 GHz for the full sample. This is consistent with the values obtained for a subsample of active galactic nuclei. For dusty sources, we find 95 per cent upper limits of 〈p2〉95 < 16.9 × 10−3 and 〈p2〉150 < 2.6 × 10−3. We find no evidence that the polarization fraction depends on the source flux or observing frequency. The 1σ upper limit on measured mean-squared polarization fraction at 150 GHz implies that extragalactic foregrounds will be subdominant to the CMB E and B mode polarization power spectra out to at least ℓ ≲ 5700 (ℓ ≲ 4700) and ℓ ≲ 5300 (ℓ ≲ 3600), respectively, at 95 (150) GHz.

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VLA Search for Optically Thick H II Regions in Luminous Embedded Infrared Sources

Symposium - International Astronomical Union ◽

10.1017/s0074180900095401 ◽

1987 ◽

Vol 115 ◽

pp. 185-186

Author(s):

Paul T.P. Ho ◽

T. N. Rengarajan

Keyword(s):

High Resolution ◽

Radio Emission ◽

High Sensitivity ◽

Radio Continuum ◽

Continuum Emission ◽

H Ii Regions ◽

Upper Limit ◽

Infrared Sources ◽

Sensitivity Maps

We have searched for radio continuum emission at 15 GHz from a number of deeply embedded protostar like infrared objects, using the B configuration of the VLA. The aim was to get high resolution (1″) and high sensitivity maps. For 10 objects (NGC 7538-IRS 3, GL 989, GL 4029-IRS 1, GL 437N, GL 2789, NGC 1333-IRS 13, S235B, GL 4029-IRS 2, R Mon and OMC2-IRS 3) we did not detect radio emission, the 3 upper limit being 0.3 – 0.5 mJy. Positive detections were made for W33A, 0MC2-IRS 4, S 235-IRS 1 and NGC 6334V-IRS 4. The cleaned maps for these objects are shown in Figures 1-4.

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H2O maser polarization of the water fountains IRAS 15445–5449 and IRAS 18043–2116

Proceedings of the International Astronomical Union ◽

10.1017/s1743921312011994 ◽

2011 ◽

Vol 7 (S283) ◽

pp. 474-475

Author(s):

Andrés F. Pérez-Sánchez ◽

Wouter H. T. Vlemmings ◽

Jessica M. Chapman

Keyword(s):

Magnetic Field ◽

Linear Polarization ◽

Infrared Image ◽

Radio Continuum ◽

Poloidal Magnetic Field ◽

Bipolar Structure ◽

Continuum Observation ◽

Low Levels ◽

The Magnetic Field ◽

Different Levels

AbstractWe present the morphology and linear polarization of the 22-GHz H2O masers in the high-velocity outflow of two post-AGB sources, d46 (IRAS 15445–5449) and b292 (IRAS 18043–2116). The observations were performed using The Australia Telescope Compact Array. Different levels of saturated maser emission have been detected for both sources. We also present the mid-infrared image of d46 overlaid with the distribution of the maser features that we have observed in the red-shifted lobe of the bipolar structure. The relative position of the observed masers and a previous radio continuum observation suggests that the continnum is produced along the blue-shifted lobe of the jet. It is likely due to synchrontron radiation, implying the presence of a strong magnetic field in the jet. The fractional polarization levels measured for the maser features of d46 indicate that the polarization vectors are tracing the poloidal component of the magnetic field in the emitting region. For the H2O masers of b292 we have measured low levels of fractional linear polarization. The linear polarization in the H2O maser region of this source likely indicates a dominant toroidal or poloidal magnetic field component.

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Extreme starlight polarization in a region with highly polarized dust emission

Astronomy and Astrophysics ◽

10.1051/0004-6361/201935266 ◽

2019 ◽

Vol 624 ◽

pp. L8 ◽

Cited By ~ 3

Author(s):

Georgia V. Panopoulou ◽

Brandon S. Hensley ◽

Raphael Skalidis ◽

Dmitry Blinov ◽

Konstantinos Tassis

Keyword(s):

Magnetic Field ◽

Dust Emission ◽

Wavelength Dependence ◽

Joint Analysis ◽

Grain Alignment ◽

Upper Limit ◽

Field Geometry ◽

Optical Wavelengths ◽

Polarization Fraction ◽

The Magnetic Field

Context. Galactic dust emission is polarized at unexpectedly high levels, as revealed by Planck. Aims. The origin of the observed ≃20% polarization fractions can be identified by characterizing the properties of optical starlight polarization in a region with maximally polarized dust emission. Methods. We measure the R-band linear polarization of 22 stars in a region with a submillimeter polarization fraction of ≃20%. A subset of 6 stars is also measured in the B, V, and I bands to investigate the wavelength dependence of polarization. Results. We find that starlight is polarized at correspondingly high levels. Through multiband polarimetry we find that the high polarization fractions are unlikely to arise from unusual dust properties, such as enhanced grain alignment. Instead, a favorable magnetic field geometry is the most likely explanation, and is supported by observational probes of the magnetic field morphology. The observed starlight polarization exceeds the classical upper limit of [pV/E(B−V)]max = 9% mag−1 and is at least as high as 13% mag−1, as inferred from a joint analysis of Planck data, starlight polarization, and reddening measurements. Thus, we confirm that the intrinsic polarizing ability of dust grains at optical wavelengths has long been underestimated.

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