2019ApJ...876...98V

To place meaningful constraints on Big Bang Nucleosynthesis models, the primordial helium abundance determination is crucial. Low-metallicity H II regions have been used to estimate it because their statistical uncertainties are relatively small. We present a new determination of the primordial helium abundance, based on long-slit spectra of the H II region NGC 346 in the small Magellanic cloud. We obtained spectra using three 409'' x 0.51'' slits divided into 97 subsets. They cover the range λλ3600-7400 of the electromagnetic spectrum. We used PyNeb and standard reduction procedures to determine the physical conditions and chemical composition. We found that for NGC 346 X = 0.7465, Y = 0.2505, and Z = 0.0030. By assuming ΔY/ΔO = 3.3 ± 0.7 we found that the primordial helium abundance is Y_P = 0.2451 ± 0.0026 (1σ). Our Y_P value is in agreement with the value of neutrino families, N_ν, and with the neutron half-life time, τ_n, obtained in the laboratory.