Magnetic braking and ambipolar diffusion in metal-poor protostars

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.