Sign on

SAO/NASA ADS Astronomy Abstract Service

· Find Similar Abstracts (with default settings below)
· Full Refereed Journal Article (PDF/Postscript)
· Full Refereed Scanned Article (GIF)
· arXiv e-print (arXiv:0710.3558)
· References in the article
· Citations to the Article (41) (Citation History)
· Refereed Citations to the Article
· SIMBAD Objects (3)
· Also-Read Articles (Reads History)
·
· Translate This Page
Title:
Magnetic fields and the dynamics of spiral galaxies
Authors:
Dobbs, C. L.; Price, D. J.
Affiliation:
AA(School of Physics, University of Exeter, Stocker Road, Exeter EX4 4QL), AB(School of Physics, University of Exeter, Stocker Road, Exeter EX4 4QL)
Publication:
Monthly Notices of the Royal Astronomical Society, Volume 383, Issue 2, pp. 497-512. (MNRAS Homepage)
Publication Date:
01/2008
Origin:
MNRAS
Astronomy Keywords:
MHD , ISM: clouds , galaxies: magnetic fields , galaxies: spiral , galaxies: structure
DOI:
10.1111/j.1365-2966.2007.12591.x
Bibliographic Code:
2008MNRAS.383..497D

Abstract

We investigate the dynamics of magnetic fields in spiral galaxies by performing 3D magnetohydrodynamics simulations of galactic discs subject to a spiral potential using cold gas, warm gas and a two-phase mixture of both. Recent hydrodynamic simulations have demonstrated the formation of interarm spurs as well as spiral arm molecular clouds, provided the interstellar medium model includes a cold HI phase. We find that the main effect of adding a magnetic field to these calculations is to inhibit the formation of structure in the disc. However, provided a cold phase is included, spurs and spiral arm clumps are still present if β >~ 0.1 in the cold gas. A caveat to the two-phase calculations though is that by assuming a uniform initial distribution, β >~ 10 in the warm gas, emphasizing that models with more consistent initial conditions and thermodynamics are required. Our simulations with only warm gas do not show such structure, irrespective of the magnetic field strength.

Furthermore, we find that the introduction of a cold HI phase naturally produces the observed degree of disorder in the magnetic field, which is again absent from simulations using only warm gas. Whilst the global magnetic field follows the large-scale gas flow, the magnetic field also contains a substantial random component that is produced by the velocity dispersion induced in the cold gas during the passage through a spiral shock. Without any cold gas, the magnetic field in the warm phase remains relatively well ordered apart from becoming compressed in the spiral shocks. Our results provide a natural explanation for the observed high proportions of disordered magnetic field in spiral galaxies and we thus predict that the relative strengths of the random and ordered components of the magnetic field observed in spiral galaxies will depend on the dynamics of spiral shocks.

Printing Options

Print whole paper
Print Page(s) through

Return 600 dpi PDF to Acrobat/Browser. Different resolutions (200 or 600 dpi), formats (Postscript, PDF, etc), page sizes (US Letter, European A4, etc), and compression (gzip,compress,none) can be set through the Printing Preferences


More Article Retrieval Options

HELP for Article Retrieval
Bibtex entry for this abstract   Preferred format for this abstract (see Preferences)
  New!

Find Similar Abstracts:

Use: Authors
Title
Keywords (in text query field)
Abstract Text
Return: Query Results Return    items starting with number
Query Form
Database: Astronomy
Physics
arXiv e-prints