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Why we need to measure turbulent magnetic fields in HII regions

Published online by Cambridge University Press:  01 November 2008

John E. Beckman  and
Mónica Relaño
John E. Beckman
Affiliation:
Instituto de Astrofísica de Canarias, Calle Vía Láctea s/n, E-38200 La Laguna, Tenerife, Spain email: jeb@iac.es Consejo Superior de Investigaciones Científicas, Madrid, Spain
Mónica Relaño
Affiliation:
Instituto de Astrofísica de Canarias, Calle Vía Láctea s/n, E-38200 La Laguna, Tenerife, Spain email: jeb@iac.es Departamento de Física Teóretica y del Cosmos, Universidad de Granada, Spain Institute of Astronomy, University of Cambridge, UK email: mrelano@ast.cam.ac.uk
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Abstract

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We have measured the emission line profiles in Hα from populations of HII regions in nearby spiral galaxies, and extracted their non-thermal line widths. These are supersonic for the more luminous regions. We infer from plots of line width, σ, against Hα luminosity, a set of regions in virial equilibrium, and derive their masses summing all known components. The virial masses are considerably larger. If this discrepancy, and the supersonic line widths, are due to the presence of magnetic fields, we can estimate their strengths at a few microgauss. Observational confirmation is clearly required.

Keywords

regions – magnetic fields – turbulence
Type
Contributed Papers
Information
Proceedings of the International Astronomical Union , Volume 4 , Symposium S259: Cosmic Magnetic Fields: From Planets, to Stars and Galaxies , November 2008 , pp. 541 - 542
Copyright
Copyright © International Astronomical Union 2009

References

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