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A new determination of the primordial helium abundance using the analyses of H II region spectra from SDSS
The precision measurement of the primordial helium abundance Yp is a powerful probe of the early Universe. The most common way to determine Yp is the analyses of observations of metal-poor H II regions found in blue compact dwarf galaxies. We present the spectroscopic sample of 100 H II regions collected from the Sloan Digital Sky Survey. The final analysed sample consists of our sample and HeBCD data base from Izotov et al. (2007). We use a self-consistent procedure to determine physical conditions, current helium abundances, and metallicities of the H II regions. From a regression to zero metallicity, we have obtained Yp = 0.2462 ± 0.0022, which is one of the most stringent constraints obtained with such methods up to date and is in a good agreement with the Planck result YPlanckp=0.2471±0.0003YpPlanck=0.2471±0.0003 . Using the determined value of Yp and the primordial deuterium abundance taken from Particle Data Group (Zyla et al. 2020) we put a constraint on the effective number of neutrino species Neff = 2.95 ± 0.16, which is consistent with the Planck one Neff = 2.99 ± 0.17. Further increase of statistics potentially allows us to achieve Planck accuracy, which in turn will become a powerful tool for studying the self-consistency of the standard cosmological model and/or physics beyond.