Nonthermal Radio Emission from Dwarf Galaxies: Do They Host Large-Scale Magnetic Fields?

  • U. Klein
  • R. Gräve

Abstract

Large spiral galaxies are usually characterized by bright nonthermal radio disks, with mostly thermal, but also nonthermal sources related to the most prominent star-forming regions, superimposed. They are massive and exhibit differential rotation, both being prerequisits for spiral structure to persist (either via density waves or via stochastic self-propagating star formation). They also contain a more or less uniform mass fraction of gas, typically 10% or less. Moreover, they were subject to constant birth rates of stars during at least the past 109 yr. The situation is fundamentally different in case of dwarf irregular galaxies. They are generally characterized by an irregular morphology, probably as a result of the lack of large-scale processes like density waves which would otherwise govern their overall appearance. They lack nonthermal radio disks, their gas-to-total mass ratios vary over a wide range, from a few percent up to almost unity. And, most characteristically, their star formation rates cannot have been constant over the past ∼ 109 yr: many of them must have been subject to bursts of star formation.

Keywords

Star Formation Radio Emission Dwarf Galaxy Star Formation Rate Small Magellanic Cloud 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

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Copyright information

© Springer-Verlag Berlin Heidelberg 1987

Authors and Affiliations

  • U. Klein
    • 1
  • R. Gräve
    • 2
  1. 1.Radioastronomisches Institut der Universität BonnBonn 1Fed. Rep. of Germany
  2. 2.Max-Planck-Institut für RadioastronomieBonn 1Fed. Rep. of Germany

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