A small-scale dynamo in feedback-dominated galaxies - III. Cosmological simulations
arXiv:1708.01486 · doi:10.1093/mnras/stx2276
Abstract
Magnetic fields are widely observed in the Universe in virtually all astrophysical objects, from individual stars to entire galaxies, even in the intergalactic medium, but their specific generation has long been debated. Due to the development of more realistic models of galaxy formation, viable scenarios are emerging to explain cosmic magnetism, thanks to both deeper observations and more efficient and accurate computer simulations. We present here a new cosmological high-resolution zoom-in magnetohydrodynamic (MHD) simulation, using the adaptive mesh refinement (AMR) technique, of a dwarf galaxy with an initially weak and uniform magnetic seed field that is amplified by a small-scale dynamo driven by supernova-induced turbulence. As first structures form from the gravitational collapse of small density fluctuations, the frozen-in magnetic field separates from the cosmic expansion and grows through compression. In a second step, star formation sets in and establishes a strong galactic fountain, self-regulated by supernova explosions. Inside the galaxy, the interstellar medium becomes highly turbulent, dominated by strong supersonic shocks, as demonstrated by the spectral analysis of the gas kinetic energy. In this turbulent environment, the magnetic field is quickly amplified via a small-scale dynamo process and is finally carried out into the circumgalactic medium by a galactic wind. This realistic cosmological simulation explains how initially weak magnetic seed fields can be amplified quickly in early, feedback-dominated galaxies, and predicts, as a consequence of the small scale dynamo process, that high-redshift magnetic fields are likely to be dominated by their small scale components.
6 pages, 6 figures, submitted to MNRAS
References in corpus (11)
- A High Order Godunov Scheme with Constrained Transport and Adaptive Mesh Refinement for Astrophysical MHD
- Escape fraction of ionizing photons during reionization: effects due to supernova feedback and runaway OB stars
- Strong magnetic fields in normal galaxies at high redshifts
- Current status of turbulent dynamo theory: From large-scale to small-scale dynamos
- Kinematic Dynamos using Constrained Transport with High Order Godunov Schemes and Adaptive Mesh Refinement
- Turbulence and Vorticity in Galaxy Clusters Generated by Structure Formation
- Cosmological MHD simulation of a cooling flow cluster
- Extragalactic Zeeman Detections in OH Megamasers
- Magnetic fields in the nearby spiral galaxy IC 342: A multi-frequency radio polarization study
- Self-similar energetics in large clusters of galaxies
- The Cosmic Microwave Background and the Ionization History of the Universe