Determination of the primordial helium abundance based on NGC 346 an HII region of the Small Magellanic Cloud
| Autor: | Valerdi, Mabel, Peimbert, Antonio, Peimbert, Manuel, Sixtos, Andrés |
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| Rok vydání: | 2019 |
| Předmět: | |
| Druh dokumentu: | Working Paper |
| DOI: | 10.3847/1538-4357/ab14e4 |
| Popis: | 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. Comment: Accepted for publication in ApJ. 9 pages, 6 figures, 9 tables |
| Databáze: | arXiv |
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