Jason Tumlinson
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Unraveling the Galaxy to Find the
Chemical abundances in long-lived, low mass Galactic halo stars
provide a unique window into star formation in the early Universe.
I present results from a new framework for calculating stochastic
chemical evolution in the full hierarchical background of Galaxy
formation that constrains the characteristic mass of primordial stars to
10 - 40 Msun. Recently evidence has begun to emerge
that
stars form in a top-heavy IMF, skewed to intermediate and high
masses, not only in gas of primordial composition but possibly up
to 1% solar metallicity. I will review these lines of
evidence and
suggest possible causes. If new predictions of this model are
borne out, the implication is that star formation during the first
billion years of cosmic history was quite different from that
around us today, with many possible consequences for the early
assembly of the Milky Way and for new observations of z > 6
galaxies planned for the James Webb Space Telescope.