Determination of the primordial helium abundance based on NGC 346 an HII
  region of the Small Magellanic Cloud
  To place meaningful constraints on Big Bang Nucleosynthesis models, the
primordial helium abundance determination is crucial. Low-metallicity HII
regions have been used to estimate it since their statistical uncertainties are
relatively small. We present a new determination of the primordial helium
abundance, based on long slit spectra of the HII region NGC 346 in the small
Magellanic cloud. We obtained spectra using three $409'' \times 0.51''$ slits
divided in 97 subsets. They cover the range $\lambda\lambda3600-7400$ 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 $\Delta Y / \Delta
O = 3.3\pm0.7$ 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 the
value of neutrino families, $N_{\nu}$, and with the neutron half-life time,
$\tau_{n}$, obtained in the laboratory.
