Astronomy and Astrophysics – Astronomy
Scientific paper
Apr 2010
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2010iaus..268..107i&link_type=abstract
Light Elements in the Universe, Proceedings of the International Astronomical Union, IAU Symposium, Volume 268, p. 107-112
Astronomy and Astrophysics
Astronomy
1
Galaxies: Abundances, Galaxies: Irregular, Galaxies: Ism, Ism: H Ii Regions, Ism: Abundances
Scientific paper
We determine the primordial helium mass fraction Yp using 1700 spectra of low-metallicity extragalactic H ii regions. This sample is selected from the Data Release 7 of the Sloan Digital Sky Survey, from European Southern Observatory archival data and from our own observations. We have considered known systematic effects which may affect the 4He abundance determination. They include collisional and fluorescent enhancements of He i recombination lines, underlying He i and hydrogen stellar absorption lines, collisional excitation of hydrogen lines, temperature and ionization structure of the H ii region. Monte Carlo methods are used to solve simultaneously the above systematic effects. We find a primordial helium mass fraction Yp = 0.2512 ± 0.0006(stat.) ± 0.0020 (syst.). This value is higher than the value given by Standard Big Bang Nucleosynthesis (SBBN) theory. If confirmed, it would imply slight deviations from SBBN.
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