http://arxiv.org/abs/1904.01594
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.
M. Valerdi, A. Peimbert, M. Peimbert, et. al.
Thu, 4 Apr 19
48/68
Comments: Accepted for publication in ApJ. 9 pages, 6 figures, 9 tables