Observations of Magnetic Fields in (Nearby) Galaxies

1994 ◽  
pp. 143-154
Author(s):  
Richard Wielebinski
Keyword(s):  
Magnetic Fields ◽  
Nearby Galaxies

scholarly journals Probing the cold magnetised Universe with SPICA-POL (B-BOP)

2019 ◽  
Vol 36 ◽  
Author(s):  
Ph. André ◽  
A. Hughes ◽  
V. Guillet ◽  
F. Boulanger ◽  
A. Bracco ◽  
...  
Keyword(s):  
Magnetic Fields ◽  
Dynamic Range ◽  
Signal To Noise Ratio ◽  
European Space Agency ◽  
Dust Emission ◽  
Far Infrared ◽  
High Dynamic Range ◽  
Wide Field ◽  
Infrared Telescope ◽  
Nearby Galaxies

Abstract Space Infrared Telescope for Cosmology and Astrophysics (SPICA), the cryogenic infrared space telescope recently pre-selected for a ‘Phase A’ concept study as one of the three remaining candidates for European Space Agency (ESA's) fifth medium class (M5) mission, is foreseen to include a far-infrared polarimetric imager [SPICA-POL, now called B-fields with BOlometers and Polarizers (B-BOP)], which would offer a unique opportunity to resolve major issues in our understanding of the nearby, cold magnetised Universe. This paper presents an overview of the main science drivers for B-BOP, including high dynamic range polarimetric imaging of the cold interstellar medium (ISM) in both our Milky Way and nearby galaxies. Thanks to a cooled telescope, B-BOP will deliver wide-field 100–350 $\mu$ m images of linearly polarised dust emission in Stokes Q and U with a resolution, signal-to-noise ratio, and both intensity and spatial dynamic ranges comparable to those achieved by Herschel images of the cold ISM in total intensity (Stokes I). The B-BOP 200 $\mu$ m images will also have a factor $\sim $ 30 higher resolution than Planck polarisation data. This will make B-BOP a unique tool for characterising the statistical properties of the magnetised ISM and probing the role of magnetic fields in the formation and evolution of the interstellar web of dusty molecular filaments giving birth to most stars in our Galaxy. B-BOP will also be a powerful instrument for studying the magnetism of nearby galaxies and testing Galactic dynamo models, constraining the physics of dust grain alignment, informing the problem of the interaction of cosmic rays with molecular clouds, tracing magnetic fields in the inner layers of protoplanetary disks, and monitoring accretion bursts in embedded protostars.

scholarly journals Radio Continuum Surveys of the Galaxy and Galaxies

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.

scholarly journals Magnetic fields in our Milky Way Galaxy and nearby galaxies

2012 ◽  
Vol 8 (S294) ◽  
pp. 213-224 ◽  
Author(s):  
JinLin Han
Keyword(s):  
Star Formation ◽  
Magnetic Fields ◽  
Large Scale ◽  
Milky Way ◽  
Spiral Galaxies ◽  
Large Scale Structure ◽  
Scale Structure ◽  
Measure Data ◽  
Submillimeter Wavelength ◽  
Nearby Galaxies

AbstractMagnetic fields in our Galaxy and nearby galaxies have been revealed by starlight polarization, polarized emission from dust grains and clouds at millimeter and submillimeter wavelength, the Zeeman effect of spectral lines or maser lines from clouds or clumps, diffuse radio synchrotron emission from relativistic electrons in interstellar magnetic fields, and the Faraday rotation of background radio sources as well as pulsars for our Milky Way. It is easy to get a global structure for magnetic fields in nearby galaxies, while we have observed many details of magnetic fields in our Milky Way, especially by using pulsar rotation measure data. In general, magnetic fields in spiral galaxies probably have a large-scale structure. The fields follow the spiral arms with or without the field direction reversals. In the halo of spiral galaxies magnetic fields exist and probably also have a large-scale structure as toroidal and poloidal fields, but seem to be slightly weaker than those in the disk. In the central region of some galaxies, poloidal fields have been detected as vertical components. Magnetic field directions in galaxies seem to have been preserved during cloud formation and star formation, from large-scale diffuse interstellar medium to molecular clouds and then to the cloud cores in star formation regions or clumps for the maser spots. Magnetic fields in galaxies are passive to dynamics.

scholarly journals Measurements of Cosmic Magnetism with LOFAR and SKA

2007 ◽  
Vol 5 ◽  
pp. 399-405 ◽  
Author(s):  
R. Beck
Keyword(s):  
Magnetic Fields ◽  
Interstellar Medium ◽  
Milky Way ◽  
Intergalactic Medium ◽  
Low Frequency ◽  
Radio Telescopes ◽  
New Era ◽  
Origin And Evolution ◽  
Central Regions ◽  
Nearby Galaxies

Abstract. The origin of magnetic fields in stars, galaxies and clusters is an open problem in astrophysics. The next-generation radio telescopes Low Frequency Array (LOFAR) and Square Kilometre Array (SKA) will revolutionize the study of cosmic magnetism. "The origin and evolution of cosmic magnetism" is a key science project for SKA. The planned all-sky survey of Faraday rotation measures (RM) at 1.4 GHz will be used to model the structure and strength of the magnetic fields in the intergalactic medium, the interstellar medium of intervening galaxies, and in the Milky Way. A complementary survey of selected regions at around 200 MHz is planned as a key project for LOFAR. Spectro-polarimetry applied to the large number of spectral channels available for LOFAR and SKA will allow to separate RM components from distinct foreground and background regions and to perform 3-D Faraday tomography of the interstellar medium of the Milky Way and nearby galaxies. – Deep polarization mapping with LOFAR and SKA will open a new era also in the observation of synchrotron emission from magnetic fields. LOFAR's sensitivity will allow to map the structure of weak, extended magnetic fields in the halos of galaxies, in galaxy clusters, and possibly in the intergalactic medium. Polarization observations with SKA at higher frequencies (1–10 GHz) will show the detailed magnetic field structure within the disks and central regions of galaxies, with much higher angular resolution than present-day radio telescopes.

scholarly journals Structure, dynamical impact and origin of magnetic fields in nearby galaxies in the SKA era

2015 ◽  
Author(s):  
Rainer Beck ◽  
Dominik Bomans ◽  
Sergio Colafrancesco ◽  
Ralf-Juergen Dettmar ◽  
Katia Ferrière ◽  
...  
Keyword(s):  
Magnetic Fields ◽  
Nearby Galaxies

scholarly journals A CCD Polarimeter with Focal Reducer

1990 ◽  
Vol 140 ◽  
pp. 252-252
Author(s):  
A. Huber
Keyword(s):  
Magnetic Fields ◽  
Radio Telescope ◽  
Angular Diameter ◽  
Nearby Galaxies ◽  
Calar Alto

At the Landessternwarte a new CCD polarimeter was constructed to observe magnetic fields (Davis-Greenstein) of nearby galaxies. This program is performed in collaboration with the MPI für Radioastronomie Bonn. By means of a focal reducer, the instrument records a field of 14.4 × 9.6 arcminutes at the 1.23-m telescope of the MPI für Astronomie on Calar Alto. Hence galaxies with large angular diameter, which have already been observed with the 100-m radio telescope Effelsberg, can be observed.

scholarly journals The Power of Low Frequencies: Faraday Tomography in the Sub-GHz Regime

Galaxies ◽  
2018 ◽  
Vol 6 (4) ◽  
pp. 112 ◽  
Author(s):  
Cameron Van Eck
Keyword(s):  
Magnetic Fields ◽  
Interstellar Medium ◽  
Frequency Dependence ◽  
Faraday Rotation ◽  
Low Frequency ◽  
Low Frequencies ◽  
Polarized Emission ◽  
Frequency Regime ◽  
Nearby Galaxies ◽  
Murchison Widefield Array

Faraday tomography, the study of the distribution of extended polarized emission by strength of Faraday rotation, is a powerful tool for studying magnetic fields in the interstellar medium of our Galaxy and nearby galaxies. The strong frequency dependence of Faraday rotation results in very different observational strengths and limitations for different frequency regimes. I discuss the role these effects take in Faraday tomography below 1 GHz, emphasizing the 100–200 MHz band observed by the Low Frequency Array and the Murchison Widefield Array. With that theoretical context, I review recent Faraday tomography results in this frequency regime, and discuss expectations for future observations.

scholarly journals CHANG-ES: XVIII—The CHANG-ES Survey and Selected Results

Galaxies ◽  
2019 ◽  
Vol 7 (1) ◽  
pp. 42 ◽  
Author(s):  
Judith Irwin ◽  
Ancor Damas-Segovia ◽  
Marita Krause ◽  
Arpad Miskolczi ◽  
Jiangtao Li ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Active Galactic Nuclei ◽  
Galactic Nuclei ◽  
Radio Continuum ◽  
Continuum Emission ◽  
Polarization Data ◽  
Wide Range ◽  
Nearby Galaxies ◽  
Broad Scale

The CHANG-ES (Continuum Halos in Nearby Galaxies) survey of 35 nearby edge-on galaxies is revealing new and sometimes unexpected and startling results in their radio continuum emission. The observations were in wide bandwidths centred at 1.6 and 6.0 GHz. Unique to this survey is full polarization data showing magnetic field structures in unprecedented detail, resolution and sensitivity for such a large sample. A wide range of new results are reported here, some never before seen in any galaxy. We see circular polarization and variability in active galactic nuclei (AGNs), in-disk discrete features, disk-halo structures sometimes only seen in polarization, and broad-scale halos with reversing magnetic fields, among others. This paper summarizes some of the CHANG-ES results seen thus far.

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