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To place meaningful constraints on Big Bang Nucleosynthesis models, theprimordial helium abundance determination is crucial. Low-metallicity HIIregions have been used to estimate it since their statistical uncertainties arerelatively small. We present a new determination of the primordial heliumabundance, based on long slit spectra of the HII region NGC 346 in the smallMagellanic cloud. We obtained spectra using three $409'' \times 0.51''$ slitsdivided in 97 subsets. They cover the range $\lambda\lambda3600-7400$ of theelectromagnetic spectrum. We used PyNeb and standard reduction procedures todetermine the physical conditions and chemical composition. We found that forNGC 346: $X=0.7465$, $Y=0.2505$ and $Z=0.0030$. By assuming $\Delta Y / \DeltaO = 3.3\pm0.7$ we found that the primordial helium abundance is $Y_{\rm P}=0.2451 \pm 0.0026$ (1$\sigma$). Our $Y_{\rm P}$ value is in agreement with thevalue of neutrino families, $N_{\nu}$, and with the neutron half-life time,$\tau_{n}$, obtained in the laboratory.

Determination of the primordial helium abundance based on NGC 346 an HII region of the Small Magellanic Cloud