3C 216: Is It the CSS Source with the Highest Rotation Measure?

AbstractWe discuss our VLBA observations at 5 and 2.7 GHz and our MERLIN observations at 1.6 and 5 GHz. A MERLIN+VLBA image provided good starting model for self-calibration and we obtained an unprecedent image of the bent jet of 3C 216. Our observations suggest the detection of strong polarization position angle variation across the observing band. If this is due to Faraday rotation then 3C216 may have a four-figure observed rotation measure, which is unlikely to be due to errors in the polarization position angle calibration.

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Faraday Rotation of the Crab Pulsar Radiation

Symposium - International Astronomical Union ◽

10.1017/s0074180900007312 ◽

1971 ◽

Vol 46 ◽

pp. 118-118

Author(s):

R. N. Manchester

Keyword(s):

Faraday Rotation ◽

Radio Astronomy ◽

Crab Nebula ◽

Position Angle ◽

Crab Pulsar ◽

Astronomy Observatory ◽

Pulsar Radiation ◽

Rotation Measure ◽

The Mean ◽

The Crab Nebula

During April, 1970, the 300-ft telescope of the National Radio Astronomy Observatory was used to determine the mean polarisation of the Crab Nebula pulsar radiation at several frequencies around 400 MHz. The position angle of the highly polarised precursor measured at each frequency, corrected for ionospheric Faraday rotation and plotted against inverse frequency squared is shown in Figure 1. The observed variation of the position angle with frequency is consistent with Faraday rotation of the plane of polarisation with a rotation measure of −40.5 ± 4.5 rad/m2. This value is of the same sign but larger than the rotation measure for the nebular radiation in the vicinity of the pulsar.

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Magnetic field at a jet base: extreme Faraday rotation in 3C 273 revealed by ALMA

Astronomy and Astrophysics ◽

10.1051/0004-6361/201832587 ◽

2019 ◽

Vol 623 ◽

pp. A111 ◽

Cited By ~ 6

Author(s):

T. Hovatta ◽

S. O’Sullivan ◽

I. Martí-Vidal ◽

T. Savolainen ◽

A. Tchekhovskoy

Keyword(s):

Magnetic Field ◽

Faraday Rotation ◽

Position Angle ◽

High Angular Resolution ◽

Systematic Uncertainties ◽

Rotation Measure ◽

Linearly Polarized ◽

Polarization Fraction ◽

The Magnetic Field ◽

Quasar 3C 273

Aims. We studied the polarization behavior of the quasar 3C 273 over the 1 mm wavelength band at ALMA with a total bandwidth of 7.5 GHz across 223–243 GHz at 0.8′′ resolution, corresponding to 2.1 kpc at the distance of 3C 273. With these observations we were able to probe the optically thin polarized emission close to the jet base, and constrain the magnetic field structure. Methods. We computed the Faraday rotation measure using simple linear fitting and Faraday rotation measure synthesis. In addition, we modeled the broadband behavior of the fractional Stokes Q and U parameters (qu-fitting). The systematic uncertainties in the polarization observations at ALMA were assessed through Monte Carlo simulations. Results. We find the unresolved core of 3C 273 to be 1.8% linearly polarized. We detect a very high rotation measure (RM) of (5.0 ± 0.3) × 105 rad m−2 over the 1 mm band when assuming a single polarized component and an external RM screen. This results in a rotation of >40° of the intrinsic electric vector position angle, which is significantly higher than typically assumed for millimeter wavelengths. The polarization fraction increases as a function of wavelength, which according to our qu-fitting could be due to multiple polarized components of different Faraday depth within our beam or to internal Faraday rotation. With our limited wavelength coverage we cannot distinguish between the cases, and additional multifrequency and high angular resolution observations are needed to determine the location and structure of the magnetic field of the Faraday active region. Comparing our RM estimate with values obtained at lower frequencies, the RM increases as a function of observing frequency, following a power law with an index of 2.0 ± 0.2, consistent with a sheath surrounding a conically expanding jet. We also detect ~0.2% circular polarization, although further observations are needed to confirm this result.

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Changes in Polarization Position Angle across the Eclipse in the Double Pulsar System

Proceedings of the International Astronomical Union ◽

10.1017/s1743921313000021 ◽

2012 ◽

Vol 8 (S291) ◽

pp. 580-582

Author(s):

R. Yuen ◽

R. N. Manchester ◽

M. Burgay ◽

F. Camilo ◽

M. Kramer ◽

...

Keyword(s):

Radio Telescope ◽

Faraday Rotation ◽

Position Angle ◽

Charge Densities

AbstractWe investigate the changes in polarization position angle in radiation from pulsar A around the eclipse in the Double Pulsar system PSR J0737-3039A/B at the 20 cm and 50 cm wavelengths using the Parkes 64-m radio telescope. The changes are ~ 2σ during and shortly after the eclipse at 20 cm but less significant at 50 cm. We show that the changes in position angle during the eclipse can be modelled by differential synchrotron absorption in the eclipse regions. Position angle changes after the eclipse are interpreted as Faraday rotation in the magnetotail of pulsar B. Implied charge densities are consistent with the Goldreich-Julian density, suggesting that the particle energies in the magnetotail are mildly relativistic.

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Radio continuum of galaxies with H2O megamaser disks

Proceedings of the International Astronomical Union ◽

10.1017/s174392131701095x ◽

2017 ◽

Vol 13 (S336) ◽

pp. 139-140

Author(s):

F. Kamali ◽

C. Henkel ◽

A. Brunthaler ◽

C. M. V. Impellizzeri ◽

K. M. Menten ◽

...

Keyword(s):

Black Hole ◽

Accretion Disk ◽

Active Galactic Nucleus ◽

Position Angle ◽

Radio Continuum ◽

Supermassive Black Hole ◽

5 Ghz

AbstractIn our attempt to investigate the basic active galactic nucleus (AGN) paradigm requiring a centrally located supermassive black hole (SMBH), a close to Keplerian accretion disk and a jet perpendicular to its plane, we have searched for radio continuum in galaxies with H2O megamasers in their disks. We observed 18 such galaxies with the Very Large Baseline Array in C band (5 GHz, ~2 mas resolution) and we detected 5 galaxies at 8 σ or higher levels. For those sources for which the maser data is available, the positions of masers and those of the 5 GHz radio continuum sources coincide within the uncertainties, and the radio continuum is perpendicular to the maser disk’s orientation within the position angle uncertainties.

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STATIONARY SHEATH OF FARADAY ROTATION IN THE JET OF 3C 120

International Journal of Modern Physics D ◽

10.1142/s0218271810016877 ◽

2010 ◽

Vol 19 (06) ◽

pp. 917-922

Author(s):

JOSÉ L. GÓMEZ ◽

MAR ROCA-SOGORB ◽

IVÁN AGUDO ◽

ALAN P. MARSCHER ◽

SVETLANA G. JORSTAD

Keyword(s):

Magnetic Field ◽

Faraday Rotation ◽

Radio Galaxy ◽

External Medium ◽

Degree Of Polarization ◽

Polarization Structure ◽

Rotation Measure ◽

Helical Magnetic Field ◽

3C 120 ◽

Two Fluid

We present a sequence of 12 monthly polarimetric multi-frequency VLBA observations of the radio galaxy 3C 120. The motion of multiple superluminal components allows the mapping of the polarization structure along most of the jet and across its width, revealing a coherent in time Faraday screen and RM-corrected polarization angles. Gradients in Faraday rotation and degree of polarization across the jet are observed, together with a localized region of high rotation measure superposed on this structure. This is explained as produced by the presence of a helical magnetic field in a two-fluid jet model, consisting of an inner emitting jet and a sheath containing nonrelativistic electrons. Interaction of the jet with the external medium would explain the confined region of enhanced Faraday rotation.

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Faraday rotation measures of Northern hemisphere pulsars using CHIME/Pulsar

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/staa1658 ◽

2020 ◽

Vol 496 (3) ◽

pp. 2836-2848 ◽

Cited By ~ 2

Author(s):

C Ng ◽

A Pandhi ◽

A Naidu ◽

E Fonseca ◽

V M Kaspi ◽

...

Keyword(s):

Northern Hemisphere ◽

Faraday Rotation ◽

Large Scale ◽

Galactic Plane ◽

High Signal ◽

First Year ◽

Systematic Analysis ◽

Intensity Mapping ◽

Rotation Measure ◽

High Cadence

ABSTRACT Using commissioning data from the first year of operation of the Canadian Hydrogen Intensity Mapping Experiment’s (CHIME) Pulsar backend system, we conduct a systematic analysis of the Faraday Rotation Measure (RM) of the Northern hemisphere pulsars detected by CHIME. We present 55 new RMs as well as obtain improved RM uncertainties for 25 further pulsars. CHIME’s low observing frequency and wide bandwidth between 400 and 800 MHz contribute to the precision of our measurements, whereas the high cadence observation provides extremely high signal-to-noise co-added data. Our results represent a significant increase of the pulsar RM census, particularly regarding the Northern hemisphere. These new RMs are for sources that are located in the Galactic plane out to 10 kpc, as well as off the plane to a scale height of ∼16 kpc. This improved knowledge of the Faraday sky will contribute to future Galactic large-scale magnetic structure and ionosphere modelling.

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An In-depth Investigation of Faraday Depth Spectrum Using Synthetic Observations of Turbulent MHD Simulations

Galaxies ◽

10.3390/galaxies7040089 ◽

2019 ◽

Vol 7 (4) ◽

pp. 89 ◽

Cited By ~ 1

Author(s):

Aritra Basu ◽

Andrew Fletcher ◽

Sui Ann Mao ◽

Blakesley Burkhart ◽

Rainer Beck ◽

...

Keyword(s):

Faraday Rotation ◽

Turbulent Medium ◽

Line Of Sight ◽

Synchrotron Emission ◽

Mhd Turbulence ◽

Broad Bandwidth ◽

Mhd Simulations ◽

Rotation Measure ◽

Spread Function ◽

Pass Through

In this paper, we present a detailed analysis of the Faraday depth (FD) spectrum and its clean components obtained through the application of the commonly used technique of Faraday rotation measure synthesis to analyze spectro-polarimetric data. To directly compare the Faraday depth spectrum with physical properties of a magneto-ionic medium, we generated synthetic broad-bandwidth spectro-polarimetric observations from magnetohydrodynamic (MHD) simulations of a transonic, isothermal, compressible turbulent medium. We find that correlated magnetic field structures give rise to a combination of spiky, localized peaks at certain FD values, and broad structures in the FD spectrum. Although most of these spiky FD structures appear narrow, giving an impression of a Faraday thin medium, we show that they arise from strong synchrotron emissivity at that FD. Strong emissivity at a FD can arise because of both strong spatially local polarized synchrotron emissivity at a FD or accumulation of weaker emissions along the distance through a medium that have Faraday depths within half the width of the rotation measure spread function. Such a complex Faraday depth spectrum is a natural consequence of MHD turbulence when the lines of sight pass through a few turbulent cells. This therefore complicates the convention of attributing narrow FD peaks to the presence of a Faraday-rotating medium along the line of sight. Our work shows that it is difficult to extract the FD along a line of sight from the Faraday depth spectrum using standard methods for a turbulent medium in which synchrotron emission and Faraday rotation occur simultaneously.

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5 GHz EVN Polarization of 3C286

Symposium - International Astronomical Union ◽

10.1017/s0074180900080128 ◽

1996 ◽

Vol 175 ◽

pp. 85-87 ◽

Cited By ~ 1

Author(s):

D. Dallacasa ◽

R.T. Schilizzi ◽

H.S. Sanghera ◽

D.R. Jiang ◽

E. Lüdke ◽

...

Keyword(s):

Electric Field ◽

Radio Source ◽

Field Vector ◽

Central Component ◽

Electric Field Vector ◽

Powerful Radio ◽

Line System ◽

Rotation Measure ◽

Polarized Emission ◽

5 Ghz

3C286 (1328+307) is a powerful radio source identified with a quasar at z=0.849. There is a foreground galaxy responsible for an H I absorption line system at z=0.6922 (Brown & Roberts 1973), centered approximately 2.″5 to the southeast of 3C286. The radio source has a steep spectrum (α = −0.61, Sv ∝ vα between 1.4 and 15 GHz) which turns over at about 100 MHz. Subarcsecond resolution radio images show a misaligned triple structure, dominated by the central component (Spencer et al. 1989) which accounts for at least 95% of the total flux density at all frequencies. 3C286 is one of the strongest extragalactic sources in polarized emission (0.84 Jy at 5 GHz and 1.41 Jy at 1.4 GHz) and with a rotation measure close to 0 rad m–2 (Rudnick and Jones 1983). Hence the observed orientation of the electric field vector is essentially independent of frequency.

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SNR Polarization and the Direction of the Magnetic Field

International Astronomical Union Colloquium ◽

10.1017/s0252921100102647 ◽

1988 ◽

Vol 101 ◽

pp. 351-354

Author(s):

D.K. Milne

Keyword(s):

Magnetic Field ◽

Faraday Rotation ◽

5 Ghz ◽

The Magnetic Field ◽

Csiro Division

AbstractAt the CSIRO Division of Radiophysics we are currently engaged in a program to map polarization in SNRs at 8.4 GHz. These results are compared with earlier Parkes 5 GHz maps to deduce the direction of magnetic field, Faraday rotation and depolarization.

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