Kavli Affiliate: Alexander P. Ji
| First 5 Authors: Kaley Brauer, Jennifer Mead, John H. Wise, Greg L. Bryan, Mordecai-Mark Mac Low
| Summary:
We explore the effect of variations in the Population III (Pop III) initial
mass function (IMF) and star-by-star feedback on early galaxy formation and
evolution using the Aeos simulations. We compare simulations with two different
Pop III IMFs: $M_text{char} = 10 , mathrm{M}_odot$ and $M_{rm max} = 100
, mathrm{M}_odot$ (Aeos10) and $M_text{char} = 20 , mathrm{M}_odot$ and
$M_{rm max} = 300 , mathrm{M}_odot$ (Aeos20). Aeos20 produces significantly
more ionizing photons, ionizing 30% of the simulation volume by $z approx 14$,
compared to 9% in Aeos10. This enhanced ionization suppresses galaxy formation
on the smallest scales. Differences in Pop III IMF also affect chemical
enrichment. Aeos20 produces Population II (Pop II) stars with higher
abundances, relative to iron, of light and $alpha$-elements, a stronger
odd-even effect, and a higher frequency of carbon-enhanced metal-poor stars.
The abundance scatter between different Pop II galaxies dominates the
differences due to Pop III IMF, though, implying a need for a larger sample of
Pop II stars to interpret the impact of Pop III IMF on early chemical
evolution. We also compare the Aeos simulations to traditional simulations that
use single stellar population particles. We find that star-by-star modeling
produces a steeper mass-metallicity relation due to less bursty feedback. These
results highlight the strong influence of the Pop III IMF on early galaxy
formation and chemical evolution, emphasizing the need to account for IMF
uncertainties in simulations and the importance of metal-poor Pop II stellar
chemical abundances when studying the first stars.
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