Strong magnetic fields and cosmic rays in very young galaxies

Abstract

We present a scenario for efficient magnetization of very young galaxies about 0.5 Gigayears after the Big-Bang by a cosmic ray-driven dynamo. These objects experience a phase of strong star formation during this first $10^9$ years. We transfer the knowledge of the connection between star formation and the production rate of cosmic rays by supernova remnants to such high redshift objects. Since the supernova rate is a direct measure for the production rate of cosmic rays we conclude that very young galaxies must be strong sources of cosmic rays. The key argument of our model is the finding that magnetic fields and cosmic rays are dynamically coupled, i.e. a strong cosmic ray source contains strong magnetic fields since the relativistic particles drive an efficient dynamo in a galaxy via their buoyancy. We construct a phenomenological model of a dynamo driven by buoyancy of cosmic rays and show that if azimuthal shearing is strong enough the dynamo amplification timescale is close to the buoyancy timescale of the order of several $10^7÷10^8$ yr. We predict that young galaxies are strongly magnetized and may contribute significantly to the gamma-ray-background.

9 pages, 1 figure, accepted for Astronomy and Astrophysics

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Cited by in corpus (13)

• A non-ideal MHD Gadget: Simulating massive galaxy clusters
• Amplification of Galactic Magnetic Fields by the Cosmic-Ray Driven Dynamo
• Origin of strong magnetic fields in Milky-Way like galactic haloes
• Cosmic ray driven dynamo in galactic disks. A parameter study
• On the magnetic fields in voids
• Magnetic field structure due to the global velocity field in spiral galaxies
• Simulations of cosmic ray propagation
• Seed fields for galactic dynamos by the magnetorotational instabilities
• Magnetic buoyancy in simulated galactic discs with a realistic circum galactic medium
• On the origin of magnetic driven winds and the structure of the galactic dynamo in isolated galaxies
• On the small scale turbulent dynamo in the intracluster medium: A comparison to dynamo theory
• Numerical dependencies of the galactic dynamo in isolated galaxies with SPH
• Multi-scale simulations of particle acceleration in astrophysical systems