The Square Kilometre Array: a new probe of cosmic magnetism

Abstract

Magnetic fields are a fundamental part of many astrophysical phenomena, but the evolution, structure and origin of magnetic fields are still unresolved problems in physics and astrophysics. When and how were the first fields generated? Are present-day magnetic fields the result of standard dynamo action, or do they represent rapid or recent field amplification through other processes? What role do magnetic fields play in turbulence, cosmic ray acceleration and structure formation? I explain how the Square Kilometre Array (SKA), a next-generation radio telescope, can deliver stunning new data-sets that will address these currently unanswered issues. The foundation for these experiments will be an all-sky survey of rotation measures, in which Faraday rotation toward > 10 7 background sources will provide a dense grid for probing magnetism in the Milky Way, nearby galaxies, and in distant galaxies, clusters and protogalaxies. Using these data, we can map out the evolution of magnetized structures from redshifts z > 3 to the present, can distinguish between different origins for seed magnetic fields in galaxies, and can develop a detailed model of the magnetic field geometry of the intergalactic medium and of the overall Universe. In addition, the SKA will certainly discover new magnetic phenomena beyond what we can currently predict or imagine.

Probing magnetic turbulence by synchrotron polarimetry: statistics and structure of magnetic fields from Stokes correlators

“…This work is an attempt to pave the way towards analysing the large amount of existing and upcoming radio‐synchrotron observational data (see e.g. Enßlin et al 2006; Gaensler 2006; Beck 2008) with the aim of achieving a better understanding of the nature of magnetized turbulence in cosmic plasmas.…”

Non-Gaussian features of primordial magnetic fields in power-law inflation

“…We expect two classes of experiments may be sensitive to this primordial non-gaussianity: deep-field all-sky Faraday rotation measures and polarization detection of the CMB. For the first class of experiments, examples are SKA [29][30][31] and LOFAR [29,32] which have projected sensitives close to 10 −10 G. In the SKA experiment, the relevant effect arises from the fact that R is directly proportional to the dark matter contrast, hence RB 2 constitutes the primordial cross correlation of matter density and cosmic magnetic fields. Preliminary searches and studies of this correlation include the Refs.…”

Science at Very High Angular Resolution with the Square Kilometre Array

“…Wavelet tomography using a grid of thousands of pulsars with known rotation measures (RMs), dispersion measures (DMs) and distances will provide the best possible map of the Galactic magnetic field and electron density on large (\100 pc) scales (Stepanov et al 2002;Noutsos 2009;Gaensler et al 2004;Gaensler 2006). So far discussions about mapping the Milky Way magnetic field using pulsars have concentrated on the ability to search for and identify many thousands of pulsars, but the importance of high angular resolution has not been emphasised.…”