Open AccessTwo populations of metal‐free stars in the early Universe
Author(s) -
Greif Thomas H.,
Bromm Volker
Publication year - 2006
Publication title -
monthly notices of the royal astronomical society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.058
H-Index - 383
eISSN - 1365-2966
pISSN - 0035-8711
DOI - 10.1111/j.1365-2966.2006.11017.x
Subject(s) - physics , reionization , astrophysics , stars , star formation , population , redshift , astronomy , initial mass function , cosmic microwave background , universe , big bang (financial markets) , galaxy , anisotropy , demography , finance , quantum mechanics , sociology , economics
We construct star formation histories at redshifts z ≳ 5 for two physically distinct populations of primordial, metal‐free stars, motivated by theoretical and observational arguments that have hinted towards the existence of an intermediate stellar generation between Population III and Population I/II. Taking into account the cosmological parameters as recently revised by the Wilkinson Microwave Anisotropy Probe after three years of operation, we determine self‐consistent reionization histories and discuss the resulting chemical enrichment from these early stellar generations. We find that the bulk of ionizing photons and heavy elements produced at high redshifts must have originated in Population II.5 stars, which formed out of primordial gas in haloes with virial temperatures ≳10 4 K, and had typical masses ≳10 M ⊙ . Classical Population III stars, formed in minihaloes and having masses ≳100 M ⊙ , on the other hand, had only a minor impact on reionization and early metal enrichment. Specifically, we conclude that only ≃10 per cent by mass of metal‐free star formation went into Population III.