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The First Stars and Galaxies: Challenges for the Next Decade Participants
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Poster
Title: Magnetic Fields: Reionization Constraints and Implications for the First Stars Author(s): Dominik Schleicher Abstract: Magnetic fields appear to be ubiquitous in the local universe, and even normal galaxies at z=4 appear to have magnetic fields similar to the Milky Way. From the epoch of recombination, an upper limit of 3 nG (comoving) exists from CMB measurements, but no there are no direct measurements. A variety of particle physics models predicts the generation of primordial magnetic fields, in particular during inflation in the electroweak and the QCD phase transitions. We discuss the evolution of magnetic fields produced before recombination and their implications for the post-recombination era, the epoch of reionization and the formation of the first stars. As most of the gas is neutral at these early times, a non-ideal MHD treatment is required that takes into account magnetic energy dissipation via ambipolar diffusion. For a comoving field strength larger than 0.3 nG, the additional heating may suppress gas collapse in the first minihalos. For the first stars, the fragmentation mass scale is unchanged, but the temperature rises at densities larger than 10^3/cm^3, which may give rise to larger accretion rates.
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