%0 Generic %1 citeulike:13640705 %A Rieder, Michael %A Teyssier, Romain %D 2015 %K imported %T A small-scale dynamo in feedback-dominated galaxies as the origin of cosmic magnetic fields. I-the kinematic phase %U http://arxiv.org/abs/1506.00849 %X Astrophysical dynamo theories provide various mechanisms for magnetic field amplification inside galaxies, where weak initial fields grow exponentially on various timescales. We investigate the particular role played by stellar feedback mechanisms in creating strong fluid turbulence, allowing for a magnetic dynamo to emerge. Performing magnetohydrodynamic simulations of isolated cooling halos, for both dwarf and Milky Way sized objects, we compare the magnetic field evolution for various initial field topologies and various stellar feedback mechanisms. We find that feedback can indeed drive strong gas turbulence which gives rise to a fast exponential magnetic field growth. Our simulations feature typical properties of Kolmogorov turbulence with a \$k ^-5/3\$ kinetic energy spectrum, as well as the characteristic properties of a small-scale dynamo, with a \$k^3/2\$ magnetic energy spectrum as predicted by Kazantsev dynamo theory. In these feedback-dominated galaxies, stellar feedback provides forcing on large scales close to the halo scale radius, providing thus exponential field growth on all scales within the galaxy. We also investigate simulations with a final quiescent phase by manually turning off the feedback. As turbulence decreases, the galactic fountain settles into a thin, rotationally supported disk. The magnetic field develops a large-scale, well-ordered structure with quadrupole symmetry, irrespective of the initial field topology, which is in good agreement with magnetic field observations of nearby spirals. Our findings suggest that weak initial seed fields were first amplified by a small-scale dynamo during a violent, feedback-dominated early phase in the galaxy formation history, followed by a more quiescent evolution, where the fields have slowly decayed or were maintained via large-scale dynamo action.

@misc{citeulike:13640705, abstract = {Astrophysical dynamo theories provide various mechanisms for magnetic field amplification inside galaxies, where weak initial fields grow exponentially on various timescales. We investigate the particular role played by stellar feedback mechanisms in creating strong fluid turbulence, allowing for a magnetic dynamo to emerge. Performing magnetohydrodynamic simulations of isolated cooling halos, for both dwarf and Milky Way sized objects, we compare the magnetic field evolution for various initial field topologies and various stellar feedback mechanisms. We find that feedback can indeed drive strong gas turbulence which gives rise to a fast exponential magnetic field growth. Our simulations feature typical properties of Kolmogorov turbulence with a \$k ^{-5/3}\$ kinetic energy spectrum, as well as the characteristic properties of a small-scale dynamo, with a \$k^{3/2}\$ magnetic energy spectrum as predicted by Kazantsev dynamo theory. In these feedback-dominated galaxies, stellar feedback provides forcing on large scales close to the halo scale radius, providing thus exponential field growth on all scales within the galaxy. We also investigate simulations with a final quiescent phase by manually turning off the feedback. As turbulence decreases, the galactic fountain settles into a thin, rotationally supported disk. The magnetic field develops a large-scale, well-ordered structure with quadrupole symmetry, irrespective of the initial field topology, which is in good agreement with magnetic field observations of nearby spirals. Our findings suggest that weak initial seed fields were first amplified by a small-scale dynamo during a violent, feedback-dominated early phase in the galaxy formation history, followed by a more quiescent evolution, where the fields have slowly decayed or were maintained via large-scale dynamo action.}, added-at = {2019-03-25T08:20:55.000+0100}, archiveprefix = {arXiv}, author = {Rieder, Michael and Teyssier, Romain}, biburl = {https://www.bibsonomy.org/bibtex/20ee9eec955fb7ee1d354e59157eaebdd/ericblackman}, citeulike-article-id = {13640705}, citeulike-linkout-0 = {http://arxiv.org/abs/1506.00849}, citeulike-linkout-1 = {http://arxiv.org/pdf/1506.00849}, day = 2, eprint = {1506.00849}, interhash = {60037b1cbd5c4bbafaf6913a42d70880}, intrahash = {0ee9eec955fb7ee1d354e59157eaebdd}, keywords = {imported}, month = jun, posted-at = {2015-06-07 06:47:22}, priority = {2}, timestamp = {2019-03-25T08:20:55.000+0100}, title = {{A small-scale dynamo in feedback-dominated galaxies as the origin of cosmic magnetic fields. I-the kinematic phase}}, url = {http://arxiv.org/abs/1506.00849}, year = 2015 }