Statistical tests of galactic dynamo theory
arXiv:1609.05688 · doi:10.3847/1538-4357/833/1/43
Abstract
Mean-field galactic dynamo theory is the leading theory to explain the prevalence of regular magnetic fields in spiral galaxies, but its systematic comparison with observations is still incomplete and fragmentary. Here we compare predictions of mean-field dynamo models to observational data on magnetic pitch angle and the strength of the mean magnetic field. We demonstrate that a standard dynamo model produces pitch angles of the regular magnetic fields of nearby galaxies that are reasonably consistent with available data. The dynamo estimates of the magnetic field strength are generally within a factor of a few of the observational values. Reasonable agreement between theoretical and observed pitch angles generally requires the turbulent correlation time to be in the range 10-20 Myr, in agreement with standard estimates. Moreover, good agreement also requires that the ratio of the ionized gas scale height to root-mean-square turbulent velocity increases with radius. Our results thus widen the possibilities to constrain interstellar medium (ISM) parameters using observations of magnetic fields. This work is a step toward systematic statistical tests of galactic dynamo theory. Such studies are becoming more and more feasible as larger datasets are acquired using current and up-and-coming instruments.
17 pages, 9 figures, accepted for publication in ApJ
References in corpus (48)
- Astrophysical magnetic fields and nonlinear dynamo theory
- Galactic Winds
- Gaseous Galaxy Halos
- Revised equipartition & minimum energy formula for magnetic field strength estimates from radio synchrotron observations
- What is Driving the HI Velocity Dispersion?
- Strong magnetic fields in normal galaxies at high redshifts
- Magnetic fields and spiral arms in the galaxy M51
- Global properties of the HI distribution in the outer Milky Way
- HI kinematics and dynamics of Messier 31
- A Universal Neutral Gas Profile for Nearby Disk Galaxies
- Systematic bias in interstellar magnetic field estimates
- Direct simulations of a supernova-driven galactic dynamo
- Magnetic fields in barred galaxies. IV. NGC 1097 and NGC 1365
- ALMA reveals the feeding of the Seyfert 1 nucleus in NGC 1566
- Galactic dynamo and helicity losses through fountain flow
- The magnetic field of M31 from multi-wavelength radio polarization observations
- The Origin and Evolution of Cosmic Magnetism
- The supernova-regulated ISM. I. The multi-phase structure
- Galactic dynamos supported by magnetic helicity fluxes
- Magnetic helicity density and its flux in weakly inhomogeneous turbulence
- Cosmic rays and the magnetic field in the nearby starburst galaxy NGC 253: II. The magnetic field structure
- Computational aspects of astrophysical MHD and turbulence
- Analysis of spiral arms using anisotropic wavelets: gas, dust and magnetic fields in M51
- Constraining dark matter halo profiles and galaxy formation models using spiral arm morphology. I. Method outline
- Equatorial magnetic helicity flux in simulations with different gauges
- High-resolution radio continuum survey of M33: III. Magnetic fields
- Nonlinear magnetic diffusivity and alpha tensors in helical turbulence
- Spiral arm pitch angle and galactic shear rate in N-body simulations of disc galaxies
- Dust Penetrated Arm Classes: Insights from rising and falling rotation curves
- Magnetic Fields in a Sample of Nearby Spiral Galaxies
- Dynamo coefficients from local simulations of the turbulent ISM
- An observational test for correlations between cosmic rays and magnetic fields
- Characterisation of the turbulent electromotive force and its magnetically-mediated quenching in a global EULAG-MHD simulation of solar convection
- Quenching and anisotropy of hydromagnetic turbulent transport
- Non-linear galactic dynamos: A toolbox
- Quantifying Resonant Structure in NGC 6946 from Two-dimensional Kinematics
- Magnetic fields in barred galaxies. II. Dynamo models
- Dynamo saturation in direct simulations of the multi-phase turbulent interstellar medium
- Magnetic Spiral Arms and Galactic Outflows
- Global simulations of the magnetic field evolution under the influence of the cosmic-ray-driven dynamo
- The extent of magnetic fields around galaxies out to z ~ 1
- An Empirical Relation Between The Large-Scale Magnetic Field And The Dynamical Mass In Galaxies
- New scaling for the alpha effect in slowly rotating turbulence
- Helicity-Flux-Driven Alpha Effect in Laboratory and Astrophysical Plasmas
- An analytical dynamo solution for large-scale magnetic fields of galaxies
- On the magnetic quenching of mean-field effects in supersonic interstellar turbulence
- Magnetic fields in barred galaxies. V. Modelling NGC 1365
- Nonlinear Galactic Dynamos and the Magnetic Pitch Angle
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- Faraday rotation maps of disk galaxies
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- Evolving Galactic Dynamos and Fits to the Reversing Rotation Measures in the Halo of NGC 4631
- Non-linear Galactic Dynamos and the Magnetic Rädler Effect
- Derivation and precision of mean field electrodynamics with mesoscale fluctuations
- The origin of the structure of large-scale magnetic fields in disc galaxies
- Some consequences of shear on galactic dynamos with helicity fluxes
- Understanding the radio luminosity function of star-forming galaxies and its cosmological evolution
- Galactic magnetic fields II. Applying the model to nearby galaxies
- Broad-band Radio Polarimetry of disk galaxies and AGN with KAT 7