MEGATRON simulations link dwarf galaxies’ iron plateau to the first stars
MEGATRON simulations suggest that explosions of very massive first-generation stars could explain why the smallest dwarf galaxies have a similar iron abundance despite differing stellar masses. The study, published in The Open Journal of Astrophysics, predicts that about 20% of these dwarfs have much less iron; this is a model result, not a direct observation of the first stars.
Bottom line — The predicted iron-poor population could help test models of the first stars as surveys measure more dwarf galaxies.
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The simulations place the plateau at about −2.5 on the iron-to-hydrogen scale for galaxies with up to 100,000 solar masses of stars, according to the study.
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The authors attribute the plateau to pair-instability supernovae from massive Population III stars, whose iron could be retained by dark matter haloes of about 10 million solar masses.
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The predicted iron-poor tail has average iron abundances at or below −3; the authors say it could survive in satellite galaxies to the present day.
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Four simulation versions varied assumptions about later generations of stars. All reproduced the plateau, though one produced too much iron in more massive dwarfs, the paper reports.
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The simulations model a region expected to develop into a Milky Way-like galaxy and follow its evolution to about 1 billion years after the Big Bang.
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The paper notes that observed measurements of average iron abundance in ultra-faint dwarf galaxies remain sparse, making the predicted population difficult to assess.
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