Kavli Affiliate: Anna Frebel
| First 5 Authors: Anirudh Chiti, Mohammad Mardini, Guilherme Limberg, Anna Frebel, Alexander P. Ji
| Summary:
The Large Magellanic Cloud (LMC) is the Milky Way’s most massive satellite
galaxy, which only recently (~2 billion years ago) fell into our Galaxy. Since
stellar atmospheres preserve their natal cloud’s composition, the LMC’s recent
infall makes its most ancient, metal-deficient ("low-metallicity") stars unique
windows into early star formation and nucleosynthesis in a formerly distant
region of the high-redshift universe. Previously, identifying such stars in the
LMC was challenging. But new techniques have opened this window, now enabling
tests of whether the earliest element enrichment and star formation in distant,
extragalactic proto-galaxies deviated from what occurred in the proto-Milky
Way. Here we present the elemental abundances of 10 stars in the LMC with
iron-to-hydrogen ratios ranging from ~1/300th to ~1/12,000th of the Sun. Our
most metal-deficient star is 50 times more metal-deficient than any in the LMC
with available detailed chemical abundance patterns, and is likely enriched by
a single extragalactic first star supernova. This star lacks significant
carbon-enhancement, as does our overall sample, in contrast with the lowest
metallicity Milky Way stars. This, and other abundance differences, affirm that
the extragalactic early LMC experienced diverging enrichment processes compared
to the early Milky Way. Early element production, driven by the earliest stars,
thus appears to proceed in an environment-dependent manner.
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