Kavli Affiliate: Anna Frebel
| First 5 Authors: Jennifer Mead, Jennifer Mead, , ,
| Summary:
Stellar surface abundances are records of the state of the gas from which
stars formed, and thus trace how individual elements have mixed into the
surrounding medium following their ejection from stars. In this work, we test
the common assumption of instantaneous and homogeneous metal mixing during the
formation of the first Population II stars by characterizing the chemical
homogeneity of the gas in simulated star-forming environments enriched by
Population III stellar feedback. Testing the homogeneity of metal mixing in
this time period is necessary for understanding the spread of abundances in the
most metal-poor stars, and the (in)homogeneity of individual sites of star
formation. Using Aeos, a suite of star-by-star cosmological simulations, we
quantify how gas abundances change over space and time relative to Population
II stellar abundances using Mahalanobis distances, a measure of
covariance-normalized dissimilarity. We find that the homogeneous mixing
assumption holds only within $sim100$ pc of a star-forming region and $sim 7$
Myr following the star formation event. Beyond this regime, deviations between
stellar and gas abundances increase until they become indistinguishable from
assuming a homogeneous mix of metals averaged over the initial mass function.
This highlights the limited applicability of assuming instantaneous and
homogeneous mixing in realistic halo environments at high redshift. We identify
critical mixing scales that are necessary to explore chemical evolution in the
early Universe. These scales can be applied to determine the precision needed
for accurate chemical tagging of observed data and to explore parameter space
with analytical models.
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