scholarly journals Constraining models of the large scale Galactic magnetic field with WMAP5 polarization data and extragalactic rotation measure sources

2009 ◽  
Vol 2009 (07) ◽  
pp. 021-021 ◽  
Author(s):  
Ronnie Jansson ◽  
Glennys R Farrar ◽  
Andre H Waelkens ◽  
Torsten A Enßlin
Keyword(s):  
Magnetic Field ◽  
Large Scale ◽  
Galactic Magnetic Field ◽  
Polarization Data ◽  
Rotation Measure

scholarly journals Is there a left-handed magnetic field in the solar neighborhood?

2019 ◽  
Vol 621 ◽  
pp. A97 ◽  
Author(s):  
A. Bracco ◽  
S. Candelaresi ◽  
F. Del Sordo ◽  
A. Brandenburg
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Large Scale ◽  
Power Spectra ◽  
Field Structure ◽  
Solar Neighborhood ◽  
Galactic Magnetic Field ◽  
Polarization Data ◽  
Left Handed ◽  
Cross Correlations

Context. The analysis of the full-sky Planck polarization data at 850 μm revealed unexpected properties of the E- and B-mode power spectra of dust emission in the interstellar medium (ISM). The positive cross-correlations over a wide range of angular scales between the total dust intensity, T, and both E and (most of all) B modes has raised new questions about the physical mechanisms that affect dust polarization, such as the Galactic magnetic field structure. This is key both to better understanding ISM dynamics and to accurately describing Galactic foregrounds to the polarization of the cosmic microwave background (CMB). In particular, in the quest to find primordial B modes of the CMB, the observed positive cross-correlation between T and B for interstellar dust requires further investigation towards parity-violating processes in the ISM. Aims. In this theoretical paper we investigate the possibility that the observed cross-correlations in the dust polarization power spectra, and specifically the one between T and B, can be related to a parity-odd quantity in the ISM such as the magnetic helicity. Methods. We produce synthetic dust polarization data, derived from 3D analytical toy models of density structures and helical magnetic fields, to compare with the E and B modes of observations. We present several models. The first is an ideal fully helical isotropic case, such as the Arnold-Beltrami-Childress field. Second, following the nowadays favored interpretation of the T–E signal in terms of the observed alignment between the magnetic field morphology and the filamentary density structure of the diffuse ISM, we design models for helical magnetic fields wrapped around cylindrical interstellar filaments. Lastly, focusing on the observed T–B correlation, we propose a new line of interpretation of the Planck observations advocating the presence of a large-scale helical component of the Galactic magnetic field in the solar neighborhood. Results. Our analysis shows that: I) the sign of magnetic helicity does not affect E and B modes for isotropic magnetic-field configurations; II) helical magnetic fields threading interstellar filaments cannot reproduce the Planck results; and III) a weak helical left-handed magnetic field structure in the solar neighborhood may explain the T–B correlation seen in the Planck data. Such a magnetic-field configuration would also account for the observed large-scale T–E correlation. Conclusions. This work suggests a new perspective for the interpretation of the dust polarization power spectra that supports the imprint of a large-scale structure of the Galactic magnetic field in the solar neighborhood.

scholarly journals A study of the regular structure of the galactic magnetic field using WMAP5 polarization data at 22 GHz

2008 ◽  
Vol 4 (S259) ◽  
pp. 573-576 ◽  
Author(s):  
Beatriz Ruiz-Granados ◽  
J. A. Rubiño-Martín ◽  
E. Battaner
Keyword(s):  
Magnetic Field ◽  
Large Scale ◽  
Regular Structure ◽  
Distribution Functions ◽  
Likelihood Method ◽  
Galactic Magnetic Field ◽  
Polarization Data ◽  
3 Dimensional ◽  
Large Scale Magnetic Field ◽  
Parameter Values

AbstractWe study the spatial structure of the 3-dimensional large-scale pattern of the Galactic Magnetic Field using the polarization maps obtained by the WMAP satellite at 22 GHz. By using five different models of the large-scale magnetic field of the Milky Way and a model for the cosmic rays distribution, we predict the expected polarized synchrotron emission. Those maps are compared to the observed 22 GHz polarization data using a Maximum Likelihood method. For each model, we obtain the parameter values which better reproduce the data and obtain their marginal probability distribution functions. We find that the model that best reproduces the observed polarization maps is an “axisymmetric” model.

scholarly journals F. Magnetic Fields, Pulsars, X-Ray And Gamma-Ray Emission

1985 ◽  
Vol 19 (1) ◽  
pp. 431-435
Keyword(s):  
Magnetic Field ◽  
Large Scale ◽  
Gamma Ray ◽  
Logarithmic Spiral ◽  
Radio Sources ◽  
Galactic Magnetic Field ◽  
Rotation Measure ◽  
The Galaxy ◽  
Magnetic Field Model ◽  
Characteristic Features

During the triennium under review many papers reported on studies of the structure of the galactic magnetic field. Andreasyan used rotation measures (RM) of large samples of extra-galactic radio sources and pulsars (29.156.001) or radio sources (32.156.002), and Inoue and Tabara (31.156.011) used in addition optical polarization of stars to investigate the direction of the large-scale regular magnetic field. Thomson and Nelson analyse the RMs of 459 extragalactic sources (32. 161.001) to determine the best fit parameters for a galactic magnetic-field model, and find agreement with their earlier work using pulsars (27.156.009). Similarly, Sofue and Fujimoto (33.155.011) show that the characteristic features of the RM distribution on the sky are well reproduced by a model in which the magnetic field is in a bisymmetric, two-armed logarithmic spiral configuration. Finally, Welter, Perry and Kronberg (37.159.096) present a statistical analysis of the (Galaxy-corrected) residual rotation measure (RRM) of 116 QSOs.

Fluctuations in the Galactic Magnetic Field

1990 ◽  
Vol 140 ◽  
pp. 55-58
Author(s):  
James M. Cordes ◽  
Andrew Clegg ◽  
John Simonetti
Keyword(s):  
Magnetic Field ◽  
Large Scale ◽  
Measure Data ◽  
Small Scale ◽  
Radio Sources ◽  
Galactic Magnetic Field ◽  
Rotation Measure ◽  
Scale Field ◽  
Large Scale Field ◽  
The Magnetic Field

We discuss small scale structure in the Galactic magnetic field as inferred from Faraday rotation measurements of extragalactic radio sources. The rotation measure data suggest a continuum of length scales extending from parsec scales down to at least 0.01 pc and perhaps to as small as 109 cm. Such turbulence in the magnetic field comprises a reservoir of energy that is comparable to the energy in the large scale field.

scholarly journals Connecting magnetic fields from sub-galactic scale to clusters of galaxies and beyond with cosmological MHD simulations

2015 ◽  
Vol 11 (A29B) ◽  
pp. 699-699
Author(s):  
Klaus Dolag ◽  
Alexander M. Beck ◽  
Alexander Arth
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Heat Transport ◽  
Galaxy Clusters ◽  
Large Scale ◽  
High Redshift ◽  
Galactic Halos ◽  
Rotation Measure ◽  
The Magnetic Field ◽  
Good Agreement

AbstractUsing the MHD version of Gadget3 (Stasyszyn, Dolag & Beck 2013) and a model for the seeding of magnetic fields by supernovae (SN), we performed simulations of the evolution of the magnetic fields in galaxy clusters and study their effects on the heat transport within the intra cluster medium (ICM). This mechanism – where SN explosions during the assembly of galaxies provide magnetic seed fields – has been shown to reproduce the magnetic field in Milky Way-like galactic halos (Beck et al. 2013). The build up of the magnetic field at redshifts before z = 5 and the accordingly predicted rotation measure evolution are also in good agreement with current observations. Such magnetic fields present at high redshift are then transported out of the forming protogalaxies into the large-scale structure and pollute the ICM (in a similar fashion to metals transport). Here, complex velocity patterns, driven by the formation process of cosmic structures are further amplifying and distributing the magnetic fields. In galaxy clusters, the magnetic fields therefore get amplified to the observed μG level and produce the observed amplitude of rotation measures of several hundreds of rad/m2. We also demonstrate that heat conduction in such turbulent fields on average is equivalent to a suppression factor around 1/20th of the classical Spitzer value and in contrast to classical, isotropic heat transport leads to temperature structures within the ICM compatible with observations (Arth et al. 2014).

scholarly journals Probing interstellar magnetic fields with Supernova remnants

2008 ◽  
Vol 4 (S259) ◽  
pp. 75-80 ◽  
Author(s):  
Roland Kothes ◽  
Jo-Anne Brown
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Supernova Remnants ◽  
Large Scale ◽  
Galactic Plane ◽  
Field Configuration ◽  
Large Scale Magnetic Field ◽  
Rotation Measure ◽  
Field Lines ◽  
The Magnetic Field

AbstractAs Supernova remnants expand, their shock waves are freezing in and compressing the magnetic field lines they encounter; consequently we can use Supernova remnants as magnifying glasses for their ambient magnetic fields. We will describe a simple model to determine emission, polarization, and rotation measure characteristics of adiabatically expanding Supernova remnants and how we can exploit this model to gain information about the large scale magnetic field in our Galaxy. We will give two examples: The SNR DA530, which is located high above the Galactic plane, reveals information about the magnetic field in the halo of our Galaxy. The SNR G182.4+4.3 is located close to the anti-centre of our Galaxy and reveals the most probable direction where the large-scale magnetic field is perpendicular to the line of sight. This may help to decide on the large-scale magnetic field configuration of our Galaxy. But more observations of SNRs are needed.

scholarly journals Polarized radiative transfer, rotation measure fluctuations, and large-scale magnetic fields

2019 ◽  
Vol 490 (2) ◽  
pp. 1697-1713
Author(s):  
Alvina Y L On ◽  
Jennifer Y H Chan ◽  
Kinwah Wu ◽  
Curtis J Saxton ◽  
Lidia van Driel-Gesztelyi
Keyword(s):  
Magnetic Field ◽  
Radiative Transfer ◽  
Magnetic Fields ◽  
Large Scale ◽  
Longitudinal Direction ◽  
Density Fluctuations ◽  
Transport Processes ◽  
Spatial Correlations ◽  
Rotation Measure ◽  
Radiative Transfer Equations

ABSTRACT Faraday rotation measure (RM) at radio wavelengths is commonly used to diagnose large-scale magnetic fields. It is argued that the length-scales on which magnetic fields vary in large-scale diffuse astrophysical media can be inferred from correlations in the observed RM. RM is a variable which can be derived from the polarized radiative transfer equations in restrictive conditions. This paper assesses the usage of rotation measure fluctuation (RMF) analyses for magnetic field diagnostics in the framework of polarized radiative transfer. We use models of various magnetic field configurations and electron density distributions to show how density fluctuations could affect the correlation length of the magnetic fields inferred from the conventional RMF analyses. We caution against interpretations of RMF analyses when a characteristic density is ill defined, e.g. in cases of lognormal-distributed and fractal-like density structures. As the spatial correlations are generally not the same in the line-of-sight longitudinal direction and the sky plane direction, one also needs to clarify the context of RMF when inferring from observational data. In complex situations, a covariant polarized radiative transfer calculation is essential to capture all aspects of radiative and transport processes, which would otherwise ambiguate the interpretations of magnetism in galaxy clusters and larger scale cosmological structures.

scholarly journals The Rotation Measure of Background Radio Sources Seen Through the Supernova Remnant OA184 (G166.2+2.5)

1988 ◽  
Vol 101 ◽  
pp. 355-358
Author(s):  
K.-T. Kim ◽  
P.P. Kronberg ◽  
T.L. Landecker
Keyword(s):  
Magnetic Field ◽  
Supernova Remnant ◽  
Active Plasma ◽  
Radio Sources ◽  
Galactic Magnetic Field ◽  
Rotation Measure ◽  
Polarity Change ◽  
Larger Sample

AbstractRadio sources in the field of the extended SNR OA184 (G166.2+2.5) have been studied to determine the excess rotation measure (RM) arising from the SNR. Of a total of 32 radio sources observed with the VLA in the C configuration, eight are found to be polarized above 7σ The sources seen through the SNR show significantly high RM in comparison to background sources. The excess RM due to the Faraday active plasma in the SNR is estimated to be 150±20 rad m−2, which corresponds to . The sign of RMs of the sources within an area of about 2°×2° centred on the SNR shows a systematic longitudinal polarity change on either side of l ≈ 166°.2. Although a larger sample is needed to justify this, we tentatively interpret this “flip” as due to the reversal of an irregular component of the galactic magnetic field on a scale of order 100 pc.

Recent and Future Measurements of Pulsar Rotation Measures and the Structure of the Large-Scale Galactic Magnetic Field

2011 ◽  
Author(s):  
Aristeidis Noutsos ◽  
Marta Burgay ◽  
Nicolò D’Amico ◽  
Paolo Esposito ◽  
Alberto Pellizzoni ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Large Scale ◽  
Galactic Magnetic Field
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