A small-scale dynamo in feedback-dominated galaxies as the origin of cosmic magnetic fields – I. The kinematic phase

摘要: The origin and evolution of magnetic fields in the Universe is still an open question. Their observations galaxies suggest strong already at high redshift as well present time. However, neither primordial nor battery processes can account for such field strengths, which implies presence a dynamo process with rapid growth rates high-redshift subsequent maintenance against decay. We investigate particular role played by feedback mechanisms creating fluid turbulence, allowing to emerge. Performing magnetohydrodynamic simulations isolated cooling gas haloes, we compare various initial topologies stellar mechanisms. find that indeed drive turbulence action. see typical properties Kolmogorov k-5/3 kinetic energy spectrum, small-scale dynamo, k3/2 spectrum predicted Kazantsev theory. also final quiescent phase. As decreases, galactic fountain settles into thin, rotationally supported disc. develops large-scale well-ordered structure even symmetry, good agreement nearby spirals. Our findings weak seed were first amplified during violent feedback-dominated early phase galaxy formation history, followed more evolution, where have slowly decayed or maintained via