Very metal-poor stars in a cosmological context

Details Very metal-poor stars in a cosmological context Very metal-poor stars in a cosmological context

May 2009

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2009aipc.1111..155r&link_type=abstract

PROBING STELLAR POPULATIONS OUT TO THE DISTANT UNIVERSE: CEFALU 2008, Proceedings of the International Conference. AIP Conferen

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Stellar Structure, Interiors, Evolution, Nucleosynthesis, Ages, Cosmology, Star Formation

Scientific paper

New observations from the Hubble ultra deep field suggest that the star formation rate at z>7 drops off faster than previously thought. Using the newly determined star formation rate for the normal mode of PopII/I stars we compute the Thomson optical depth. We also investigate the consequences of PopIII stars on the local metallicity distribution function of the Galactic halo and on the evolution of C, O abundances as a function of [Fe/H], with special emphasis on carbon-enhanced metal-poor stars (CEMPS). The metallicity distribution function shape is well reproduced at low redshift ([Fe/H]>~-4), in agreement with other studies. However, the Hamburg/ESO survey hints at a sharp decrease of the number of low-mass stars at very low iron abundance, which is not reproduced in models with only PopII/I stars. The presence of PopIII stars helps in reproducing this feature, leading to a prompt initial enrichment before the onset of PopII/I stars. Finally, we show that the nucleosynthetic yields of PopIII stars leads to abundance patterns in agreement with those observed in extremely metal-poor stars. This can be evidenced by the transition discriminant (a criterion for low-mass star formation taking into account the cooling due to C II and O I). In this simple approach for cosmic evolution, PopIII stars prove to be a compulsory ingredient, and extremely metal poor stars are found to be born at high redshift.

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