Using SKA Rotation Measures to Reveal the Mysteries of the Magnetised Universe

Johnston‐Hollitt, M.; Govoni, F.; Beck, R.; Dehghan, Siamak; Pratley, Luke; Akahori, Takuya; Heald, G.; Agudo, I.; Bonafede, A.; Carretti, E.; Clarke, Tom; Colafrancesco, S.; Enßlin, T. A.; Feretti, L.; Gaensler, B. M.; Haverkorn, M.; Mao, S. A.; Oppermann, N.; Rudnick, L.; Scaife, Anna M. M.; Schnitzeler, Dominic; Stil, J. M.; Taylor, Andrew; Vacca, V.

doi:10.22323/1.215.0092

Cited by 50 publications

(45 citation statements)

References 75 publications

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“…The SKA "Cosmic Magnetism" Key Science Project plans to observe a polarization survey over the entire accessible sky with the SKA-MID Band 2 (around 20 cm wavelength) (Johnston-Hollitt et al 2015). Within 1 h integration per field this will allow the detection of about 10 million discrete extragalactic sources and the measurement of their RMs, about 300 RMs per square degree or a mean spacing between sources of about 3 .…”

Section: Discussionmentioning

confidence: 99%

Magnetic fields in spiral galaxies

Beck¹

2015

Astron Astrophys Rev

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Radio synchrotron emission, its polarization and Faraday rotation of the polarization angle are powerful tools to study the strength and structure of magnetic fields in galaxies. Unpolarized synchrotron emission traces isotropic turbulent fields which are strongest in spiral arms and bars (20-30 μG) and in central starburst regions (50-100 μG). Such fields are dynamically important; they affect gas flows and drive gas inflows in central regions. Polarized emission traces ordered fields, which can be regular or anisotropic turbulent, where the latter originates from isotropic turbulent fields by the action of compression or shear. The strongest ordered fields (10-15 μG) are generally found in interarm regions. In galaxies with strong density waves, ordered fields are also observed at the inner edges of spiral arms. Ordered fields with spiral patterns exist in grand-design, barred and flocculent galaxies and in central regions. Ordered fields in interacting galaxies have asymmetric distributions and are a tracer of past interactions between galaxies or with the intergalactic medium.-Faraday rotation measures of the diffuse polarized radio emission from galaxy disks reveal large-scale spiral patterns that can be described by the superposition of azimuthal modes; these are signatures of regular fields generated by mean-field dynamos. "Magnetic arms" between gaseous spiral arms may also be products of dynamo action, but need a stable spiral pattern to develop. Helically twisted field loops winding around spiral arms were found in two galaxies so far. Large-scale field reversals, like the one found in the Milky Way, could not yet be detected in external galaxies. In radio halos around edgeon galaxies, ordered magnetic fields with X-shaped patterns are observed. The origin and evolution of cosmic magnetic fields, in particular their first occurrence in young

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Section: Discussionmentioning

confidence: 99%

Magnetic fields in spiral galaxies

Beck¹

2015

Astron Astrophys Rev

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368

269

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“…For ≈ 1700 pointings over 30 000 deg 2 , the total survey time is around 10 000 hours. We note that the 1420-MHz component of this survey will simultaneously provide the data needed for observations of an RM grid (Johnston-Hollitt et al 2015).…”

Section: Survey Specificationsmentioning

confidence: 97%

“…Specifically, the RM grid remains a powerful tool for probing foreground magnetic fields, i.e., cases where the polarised emitting region and Faraday rotating medium are distinct and well separated, and where the combined statistical properties of a large number of sightlines can be used to extract the global magneto-ionic properties of intervening material (Johnston-Hollitt et al 2015).…”

Section: Introductionmentioning

confidence: 99%

Broadband Polarimetry with the Square Kilometre Array: A Unique Astrophysical Probe

Gaensler¹,

Agudo²,

Akahori³

et al. 2015

Proceedings of Advancing Astrophysics With the Square Kilometre Array — PoS(AASKA14)

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Faraday rotation of polarised background sources is a unique probe of astrophysical magnetic fields in a diverse range of foreground objects. However, to understand the properties of the polarised sources themselves and of depolarising phenomena along the line of sight, we need to complement Faraday rotation data with polarisation observations over very broad bandwidths. Just as it is impossible to properly image a complex source with limited u-v coverage, we can only meaningfully understand the magneto-ionic properties of polarised sources if we have excellent coverage in λ 2 -space. We here propose a set of broadband polarisation surveys with both SKA1 and SKA2, which will provide a singular set of scientific insights on the ways in which galaxies and their environments have evolved over cosmic time.Advancing Astrophysics with the Square Kilometre Array

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“…This will markedly improve statistics, both within individual regions, and within Galactic structures such as individual spiral arms. The increased number of measurements will allow for a comparison of maser field directions with those probed via Faraday rotation of polarized continuum sources through nearby sightlines that contain a magnetoionic medium, which will in turn be vastly improved in the SKA era through all-sky polarimetric surveys (Johnston-Hollitt 2015).…”

Section: Pos(aaska14)110mentioning

confidence: 99%

Measuring Magnetic Fields Near and Far with the SKA via the Zeeman Effect

Robishaw¹,

Green²,

Surcis³

et al. 2015

Proceedings of Advancing Astrophysics With the Square Kilometre Array — PoS(AASKA14)

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The measurement of Zeeman splitting in spectral lines-both in emission and absorption-can provide direct estimates of the magnetic field strength and direction in atomic and molecular clouds, both in our own Milky Way and in external galaxies. This method will probe the magnetic field in the warm and cold neutral components of the interstellar medium, providing a complement to the extensive SKA Faraday studies planning to probe the field in the ionized components.Advancing Astrophysics with the Square Kilometre Array

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Using SKA Rotation Measures to Reveal the Mysteries of the Magnetised Universe

Cited by 50 publications

References 75 publications

Magnetic fields in spiral galaxies

Magnetic fields in spiral galaxies

Broadband Polarimetry with the Square Kilometre Array: A Unique Astrophysical Probe

Measuring Magnetic Fields Near and Far with the SKA via the Zeeman Effect

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