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An Empirical Relation Between The Large-Scale Magnetic Field And The Dynamical Mass In Galaxies | | F. S. Tabatabaei
; T. P. K. Martinsson
; J. H. Knapen
; J. E. Beckman
; B. Koribalski
; B. G. Elmegreen
; | | Date: |
26 Dec 2015 | | Abstract: | The origin and evolution of cosmic magnetic fields as well as the influence
of the magnetic fields on the evolution of galaxies are unknown. Though not
without challenges, the dynamo theory can explain the large-scale coherent
magnetic fields which govern galaxies, but observational evidence for the
theory is so far very scarce. Putting together the available data of
non-interacting, non-cluster galaxies with known large-scale magnetic fields,
we find a tight correlation between the integrated polarized flux density and
the rotation speed, v(rot), of galaxies. This leads to an almost linear
correlation between the large-scale magnetic field B and v(rot), assuming that
the number of cosmic ray electrons is proportional to the star formation rate.
This correlation cannot be attributed to an active linear dynamo processes, as
no correlation holds with shear or angular speed. It indicates instead a
coupling between the large-scale magnetic field and the dynamical mass of the
galaxies, B~M(dyn)^{0.2-0.3}. Hence, faster rotating and/or more massive
galaxies have stronger large-scale magnetic fields. The observed B-v(rot)
correlation shows that the anisotropic turbulent magnetic field dominates B in
fast rotating galaxies as the turbulent magnetic field, coupled with gas, is
enhanced and ordered due to the strong gas compression and/or shear in these
systems. This study supports a stationary condition and no further evolution of
the large-scale magnetic field as long as the dynamical mass of galaxies is
constant. | | Source: | arXiv, 1512.8145 | | Services: | Forum | Review | PDF | Favorites | |
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