THE PRIMORDIAL ABUNDANCE OF HE-4 - AN UPDATE

Citation
Ka. Olive et al., THE PRIMORDIAL ABUNDANCE OF HE-4 - AN UPDATE, The Astrophysical journal, 483(2), 1997, pp. 788-797
Citations number
57
Categorie Soggetti
Astronomy & Astrophysics
Journal title
ISSN journal
0004637X
Volume
483
Issue
2
Year of publication
1997
Part
1
Pages
788 - 797
Database
ISI
SICI code
0004-637X(1997)483:2<788:TPAOH->2.0.ZU;2-V
Abstract
We include new data in an updated analysis of helium in low-metallicit y extragalactic H nr regions with the goal of deriving the primordial abundance of He-4 (Y-P). We show that the new observations of Izotov e t al. are consistent with previous data. However, they should not be t aken in isolation to determine Y-P, owing to the lack of sufficiently low-metallicity points. We use the extant data in a semiempirical appr oach to bounding the size of possible systematic uncertainties in the determination of Y-P. Our best estimate for the primordial abundance o f He-4 assuming a linear relation between He-4 and O/H is Y-P= 0.230 /- 0.003(stat) based on the subset of H II regions with the lowest met allicity; for our full data set we find Y-P= 0.234 +/- 0.002(stat). Bo th values are entirely consistent with our previous results. We discus s the implications of these values for standard big bang nucleosynthes is (SBBN), particularly in the context of recent measurements of deute rium in high-redshift, low-metallicity QSO absorption-line systems.