November 29 @ 10:00 am - 11:00 am
AMT Colloquium takes place every Tuesday at 10 AM virtually. Zoom link below.
Prof. Christopher F. McKee obtained his Ph.D. from the University of California, Berkeley in 1970. He is a member of the National Academy of Sciences and was elected a Legacy Fellow of the American Astronomical Society in 2020. He has developed a self-regulated model for the structure and evolution of molecular clouds, and for the rate of star formation within these clouds.
Title: Magnetic Fields in the Formation of the First Stars
Abstract: Today, stars form in Giant Molecular Clouds, but it is generally assumed that the first stars formed in dark matter mini halos. The effects of magnetic fields in contemporary star formation range from reducing fragmentation to powering protostellar outflows. The effects of magnetic fields in the formation of the first stars depend on their strength. The Biermann battery can produce fields of order 1e-19 G, and this can be amplified to of order 1e-16 G in a turbulent cascade. The field can then be amplified by many orders of magnitude by a turbulent dynamo. The breakdown of flux-freezing in the nonlinear dynamo limits the growth rate of the field in that stage; whether the field can reach equipartition with the turbulent motions depends sensitively on the parameters. We predict the results of the simulation of a cosmological dynamo simulation and compare that with the results of the first such simulation that has been carried out. The numerical viscosity is several orders of magnitude larger than the actual one so that, as noted by previous authors, the simulation is not converged. We find that magnetic fields strongly suppress fragmentation: No low-mass stars are formed in our simulation, consistent with the absence of observed Pop III stars.
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