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

## TL;DR

This study accurately measures the primordial helium abundance using spectral data from the HII region NGC 346 in the Small Magellanic Cloud, providing constraints relevant for Big Bang Nucleosynthesis models.

## Contribution

It presents a new determination of the primordial helium abundance based on detailed spectral analysis of NGC 346, improving previous estimates with high-quality data and analysis methods.

## Key findings

- Primordial helium abundance Y_P = 0.2451 ± 0.0026
- Consistent with neutrino family count and neutron lifetime
- Spectroscopic analysis of NGC 346 yields precise chemical composition

## Abstract

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.