Origin of Magnetic Field in the Intracluster Medium: Primordial or Astrophysical?

Abstract

The origin of magnetic fields in clusters of galaxies is still an unsolved problem, which is largely due to our poor understanding of initial seed magnetic fields. If the seed magnetic fields have primordial origins, it is likely that large-scale pervasive magnetic fields were present before the formation of the large-scale structure. On the other hand, if they were ejected from astrophysical bodies, they were highly localized in space at the time of injection. In this paper, using turbulence dynamo models for high magnetic Prandtl number fluids, we find constraints on the seed magnetic fields. The hydrodynamic Reynolds number based on the Spitzer viscosity in the intracluster medium (ICM) is believed to be less than $O(10^2)$, while the magnetic Reynolds number can be much larger than that. In this case, if the seed magnetic fields have primordial origins, they should be stronger than $O(10^{-11})$G, which is very close to the upper limit of $O(10^{-9})$G set by the cosmic microwave background (CMB) observations. On the other hand, if the seed magnetic fields were ejected from astrophysical bodies, any seed magnetic fields stronger than $O(10^{-9})$G can safely magnetize the intracluster medium. Therefore, it is less likely that primordial magnetic fields are the direct origin of present-day magnetic fields in the ICM.

11 pages, 10 figures, Accepted for publication in the ApJ

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• Seed magnetic fields in turbulent small-scale dynamos
• Magnetogenesis around the first galaxies: the impact of different field seeding processes on galaxy formation
• Detecting shocked intergalactic gas with X-ray and radio observations
• Evolution of primordial magnetic fields during large-scale structure formation
• Simulations and observational tests of primordial magnetic fields from Cosmic Microwave Background constraints
• Viscosity, pressure, and support of the gas in simulations of merging cool-core clusters
• Troubled cosmic flows: turbulence, enstrophy and helicity from the assembly history of the intracluster medium
• Connecting turbulent velocities and magnetic fields in galaxy cluster simulations with active galactic nuclei jets
• On the nature of LOFAR RMs and new constraints on magnetic fields in cosmic filaments and on magnetogenesis scenarios
• Limits and challenges of the detection of cluster-scale diffuse radio emission at high redshift: The Massive and Distant Clusters of WISE Survey (MaDCoWS) in LoTSS-DR2
• Galactic winds and the origin of large-scale magnetic fields
• Radio Observations as a Probe of Cosmic Web Magnetism
• On the interpretation of XRISM X-ray measurements of turbulence in the intracluster medium: a comparison with cosmological simulations
• Effective Viscosity in the Intracluster Medium During Magnetic Field Amplification via Turbulent Dynamo
• Introduction to Strong Alfvénic MHD Turbulence