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Magnetic braking and ambipolar diffusion in metal-poor protostars

Published online by Cambridge University Press:  01 November 2008

Hans Zinnecker
Hans Zinnecker*
Affiliation:
Astrophysikalisches Institut Potsdam, An der Sternwarte 16, D-14482 Potsdam, Germany email: [email protected]
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Abstract

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In this short note, we raise the issue how magnetic braking of prestellar and protostellar condensations depends on the metallicity of the molecular gas cloud. We suggest that the degree of ionization, which determines the timescale for redistribution of magnetic flux (ambipolar diffusion) in the dense cloud core, depends linearly on the heavy element and dust abundance of the gas. This implies that magnetic braking is less efficient in metal-poor condensations, and hence more of the angular momentum problem of star formation must be solved by other means, such as fragmentation into (wider) binary systems. Observations of orbital periods (separations) of binary systems among the metal-poor Galactic halo stars could test this prediction.

Keywords

Magnetic fields – diffusion – protostars – ISM: molecules
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. 113 - 114
Copyright
Copyright © International Astronomical Union 2009

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