Abstract

PEIMBERT, A.; PEIMBERT, M.  and  LURIDIANA, V.. The primordial helium abundance and the number of neutrino families. Rev. mex. astron. astrofis [online]. 2016, vol.52, n.2, pp.419-424. ISSN 0185-1101.

Based on observations of H II regions and on the new computations of the recombination coefficients of the He I lines by Porter el al. we obtain a primordial helium abundance by mass of YP = 0.2446 ± 0.0029. We consider thirteen sources of error for the YP determination; some of them are mainly due to systematic effects, while the rest are mainly due to statistical effects. We compare our results with other determinations of YP present in the literature. Combining our YP value with computations of primordial nucleosynthesis we find a number of neutrino species Neff = 2.90 ± 0.22, and a neutron mean life τν = 872 ± 14 s.

Keywords : early universe; galaxies: abundances; galaxies: ISM; H II regions; ISM: abundances.