Axions produced in supernovae generate a diffuse gamma-ray signal through conversion in magnetic fields, yielding competitive constraints on the axion-photon coupling from COMPTEL, EGRET, and Fermi-LAT data plus forecasts for future MeV telescopes.
Beck, Magnetic fields in spiral galaxies , The Astronomy and Astrophysics Review 24 (2015) 4 [1509.04522]
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abstract
Radio synchrotron emission is a powerful tool 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 \mu G) and in central starburst regions (50-100 \mu G). 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 \mu G) 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. In radio halos around edge-on galaxies, ordered magnetic fields with X-shaped patterns are observed. -- 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. -- The origin and evolution of cosmic magnetic fields will be studied with forthcoming radio telescopes like the Square Kilometre Array.
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A self-consistent Parker bound on magnetic monopoles is derived using the galactic mean-field dynamo eigenmode and turbulent field seeding and acceleration, producing modified flux limits at low and intermediate masses that are robust to primordial magnetic fields.
SPICE-RACS DR2 delivers the largest single Faraday rotation measure catalog from a radio survey, with 250,000-340,000 RMs across most of the sky at median uncertainty of 2 rad m^{-2}.
Magnetic field corrections to inspiral waveforms appear at -2 PN and -3 PN orders and mimic power-law environmental gravity but can be distinguished above a transition density of about 10^{-4} kg/m^3 for Bonnor-Melvin cases using multi-event statistics.
Superposition of static galactic magnetic dipoles is screened by intergalactic plasma and cannot account for lower bounds on magnetic fields in cosmic voids from blazar gamma-ray data.
citing papers explorer
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Lights, Camera, Axion: Tracing Axions from Supernovae in the Diffuse $\gamma$-ray Sky
Axions produced in supernovae generate a diffuse gamma-ray signal through conversion in magnetic fields, yielding competitive constraints on the axion-photon coupling from COMPTEL, EGRET, and Fermi-LAT data plus forecasts for future MeV telescopes.
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Self-Consistent Parker Bound on Magnetic Monopoles
A self-consistent Parker bound on magnetic monopoles is derived using the galactic mean-field dynamo eigenmode and turbulent field seeding and acceleration, producing modified flux limits at low and intermediate masses that are robust to primordial magnetic fields.
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The Rapid ASKAP Continuum Survey VII: Spectra and Polarisation In Cutouts of Extragalactic Sources (SPICE-RACS) Second Data Release -- Unveiling the Magnetised Sky
SPICE-RACS DR2 delivers the largest single Faraday rotation measure catalog from a radio survey, with 250,000-340,000 RMs across most of the sky at median uncertainty of 2 rad m^{-2}.
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Distinguishability of magnetic massive black holes from environmental mimics with inspiral gravitational waves
Magnetic field corrections to inspiral waveforms appear at -2 PN and -3 PN orders and mimic power-law environmental gravity but can be distinguished above a transition density of about 10^{-4} kg/m^3 for Bonnor-Melvin cases using multi-event statistics.
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On the contribution of galaxies to the magnetic field in cosmic voids
Superposition of static galactic magnetic dipoles is screened by intergalactic plasma and cannot account for lower bounds on magnetic fields in cosmic voids from blazar gamma-ray data.