Measuring magnetism in the Milky Way with the Square Kilometre Array

Haverkorn, M.; Akahori, Takuya; Carretti, E.; Ferrière, K.; Frick, Peter; Gaensler, B. M.; Heald, G.; Johnston‐Hollitt, M.; Jones, D. O.; Landecker, T. L.; Mao, Sui Ann; Noutsos, Aris; Oppermann, N.; Reich, W.; Robishaw, Timothy; Scaife, Anna M. M.; Schnitzeler, Dominic; Stepanov, Rodion; Sun, Xiaohui; Taylor, Russ

doi:10.22323/1.215.0096

Cited by 18 publications

(25 citation statements)

References 96 publications

(120 reference statements)

Supporting

Mentioning

Contrasting

Order By: Relevance

“…It is a multi-phase medium composed of a tenuous plasma that is permeated by a large-scale magnetic field and is highly turbulent (McKee & Ostriker 2007;Haverkorn et al 2015). Despite advances in theory and simulation (Burkhart et al 2012), our understanding of the properties of the ISM has been limited by the dearth of observational data against which to test.…”

Section: Introductionmentioning

confidence: 99%

Low-Frequency Observations of Linearly Polarized Structures in the Interstellar Medium Near the South Galactic Pole

Lenc

Gaensler

Sun

et al. 2016

ApJ

View full text Add to dashboard Cite

We present deep polarimetric observations at 154 MHz with the Murchison Widefield Array (MWA), covering 625 deg 2 centered on α=0 h andδ=−27°. The sensitivity available in our deep observations allows an in-band, frequency-dependent analysis of polarized structure for the first time at long wavelengths. Our analysis suggests that the polarized structures are dominated by intrinsic emission but may also have a foreground Faraday screen component. At these wavelengths, the compactness of the MWA baseline distribution provides excellent snapshot sensitivity to large-scale structure. The observations are sensitive to diffuse polarized emission at ∼54′ resolution with a sensitivity of 5.9 mJy beam −1 and compact polarized sources at ∼2 4 resolution with a sensitivity of 2.3 mJy beam −1 for a subset (400 deg 2 ) of this field. The sensitivity allows the effect of ionospheric Faraday rotation to be spatially and temporally measured directly from the diffuse polarized background. Our observations reveal large-scale structures (∼1°-8°in extent) in linear polarization clearly detectable in ∼2 minute snapshots, which would remain undetectable by interferometers with minimum baseline lengths of >110 m at 154 MHz. The brightness temperature of these structures is on average 4 K in polarized intensity, peaking at 11 K. Rotation measure synthesis reveals that the structures have Faraday depths ranging from −2 to 10 rad m −2 with a large fraction peaking at approximately+1 rad m −2 . We estimate a distance of 51±20 pc to the polarized emission based on measurements of the in-field pulsar J2330-2005. We detect four extragalactic linearly polarized point sources within the field in our compact source survey. Based on the known polarized source population at 1.4 GHz and non-detections at 154 MHz, we estimate an upper limit on the depolarization ratio of 0.08 from 1.4 GHz to 154 MHz.

show abstract

Section: Introductionmentioning

confidence: 99%

Low-Frequency Observations of Linearly Polarized Structures in the Interstellar Medium Near the South Galactic Pole

Lenc

Gaensler

Sun

et al. 2016

ApJ

View full text Add to dashboard Cite

show abstract

“…Some models of the existing observations seem to confirm the mixed parity dynamo modes (Jansson & Farrar, 2012). Characterising the global structure is, however, quite difficult due to contamination by local structures like the local magnetised bubble (Sun & Reich, 2010;Haverkorn et al, 2015).…”

Section: The Milky Waymentioning

confidence: 99%

Probing Magnetic Fields with Square Kilometre Array and its Precursors

et al. 2016

View full text Add to dashboard Cite

Origin of magnetic fields, its structure and effects on dynamical processes in stars to galaxies are not well understood. Lack of a direct probe has remained a problem for its study. The first phase of Square Kilometre Array (SKA-I), will have almost an order of magnitude higher sensitivity than the best existing radio telescope at GHz frequencies. In this contribution, we discuss specific science cases that are of interest to the Indian community concerned with astrophysical turbulence and magnetic fields. The SKA-I will allow observations of a large number of background sources with detectable polarization and measure their Faraday depths (FDs) through the Milky Way, other galaxies and their circum-galactic mediums. This will probe line-of-sight magnetic fields in these objects well and provide field configurations. Detailed comparison of observational data (e.g., pitch angles in spirals) with models which consider various processes giving rise to field amplification and maintenance (e.g., various types of dynamo models) will then be possible. Such observations will also provide the coherence scale of the fields and its random component through RM structure function. Measuring the random component is important to characterise turbulence in the medium. Observations of FDs with redshift will provide important information on magnetic field evolution as a function of redshift. The background sources could also be used to probe magnetic fields and its coherent scale in galaxy clusters and in bridges formed between interacting galaxies. Other than FDs, sensitive observations of synchrotron emission from galaxies will provide complimentary information on their magnetic field strengths in the sky plane. The core shift measurements of AGNs can provide more precise measurements of magnetic field in the sub parsec region near the black hole and its evolution. The low band of SKA-I will also be useful to study circularly polarized emission from Sun and comparing various models of field configurations with observations.

show abstract

“…Probing the 3-D Galactic magnetic field structure Our current understanding of the large-scale magnetic field structure in the Milky Way disc is that it is broadly aligned with the spiral arms and has a strength of a few µG (e.g. Haverkorn et al 2015). Recent analyses often favour an axisymmetric spiral structure with a single reversal in the field direction (e.g.…”

Section: Studying the Pulsar Magnetospherementioning

confidence: 99%

“…Han et al 2006). The 3-D field in the halo is even less well understood, with several proposed geometries (see Haverkorn et al 2015).…”

Section: Studying the Pulsar Magnetospherementioning

confidence: 99%

“…A good understanding of the antennas' polarisation performance and accurate ionospheric monitoring will be invaluable for these science cases. These data will be complementary to the 'RM grid' of extragalactic point sources and diffuse Galactic synchrotron images, towards a more comprehensive picture of the GMF (Haverkorn et al 2015).…”

Section: Summary and The Next 50 Yearsmentioning

confidence: 99%

See 1 more Smart Citation

Studying Magnetic Fields using Low-frequency Pulsar Observations

Sobey

2017

Proc. IAU

View full text Add to dashboard Cite

Low-frequency polarisation observations of pulsars, facilitated by next-generation radio telescopes, provide powerful probes of astrophysical plasmas that span many orders of magnitude in magnetic field strength and scale: from pulsar magnetospheres to intervening magneto-ionic plasmas including the ISM and the ionosphere. Pulsar magnetospheres with teragauss field strengths can be explored through their numerous emission phenomena across multiple frequencies, the mechanism behind which remains elusive. Precise dispersion and Faraday rotation measurements towards a large number of pulsars probe the three-dimensional large-scale (and eventually small-scale) structure of the Galactic magnetic field, which plays a role in many astrophysical processes, but is not yet well understood, especially towards the Galactic halo. We describe some results and ongoing work from the Low Frequency Array (LOFAR) and the Murchison Widefield Array (MWA) radio telescopes in these areas. These and other pathfinder and precursor telescopes have reinvigorated low-frequency science and build towards the Square Kilometre Array (SKA), which will make significant advancements in studies of astrophysical magnetic fields in the next 50 years.

show abstract

Measuring magnetism in the Milky Way with the Square Kilometre Array

Cited by 18 publications

References 96 publications

Low-Frequency Observations of Linearly Polarized Structures in the Interstellar Medium Near the South Galactic Pole

Low-Frequency Observations of Linearly Polarized Structures in the Interstellar Medium Near the South Galactic Pole

Probing Magnetic Fields with Square Kilometre Array and its Precursors

Studying Magnetic Fields using Low-frequency Pulsar Observations

Contact Info

Product

Resources

About