Limits on Population III star formation with the most iron-poor stars

M. de Bennassuti, S. Salvadori, R. Schneider, R. Valiante, K. Omukai

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78 Citations (Scopus)


We study the impact of star-forming minihaloes, and the initial mass function (IMF) of Population III (Pop III) stars, on the Galactic halo metallicity distribution function (MDF) and on the properties of C-enhanced and C-normal stars at [Fe/H] < -3. For our investigation we use a data-constrained merger tree model for the MilkyWay formation, which has been improved to self-consistently describe the physical processes regulating star formation in minihaloes, including the poor sampling of the Pop III IMF.We find that only when star-forming minihaloes are included the low-Fe tail of the MDF is correctly reproduced, showing a plateau that is built up by C-enhanced metal-poor stars imprinted by primordial faint supernovae. The incomplete sampling of the Pop III IMF in inefficiently star-forming minihaloes (< 10-3M yr-1) strongly limits the formation of pair-instability supernovae (PISNe), with progenitor masses mPopIII = [140-260]M, even when a flat Pop III IMF is assumed. Second-generation stars formed in environments polluted at > 50 per cent level by PISNe are thus extremely rare, corresponding to ≈0.25 per cent of the total stellar population at [Fe/H] < -2, which is consistent with recent observations. The low-Fe tail of the MDF strongly depends on the Pop III IMF shape and mass range. Given the current statistics, we find that a flat Pop III IMF model with mPopIII = [10-300]M is disfavoured by observations. We present testable predictions for Pop III stars extending down to lower masses, with mPopIII = [0.1-300]M.

Original languageEnglish
Pages (from-to)926-940
Number of pages15
JournalMonthly Notices of the Royal Astronomical Society
Issue number1
Publication statusPublished - 2017 Feb 11


  • Galaxies: ISM
  • Galaxy: evolution
  • Stars: Population II
  • Stars: Population III
  • Stars: formation
  • Supernovae: general


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