2026/01/29 by Erik Aver, Evan D. Skillman, Richard W. Pogge +7 · 1 voice
Physics and Astronomy · #astro-ph.CO
We present a new determination of the primordial helium abundance based on new, high-quality Large Binocular Telescope (LBT) observations of 54 metal-poor H II regions. These regions have been observed and analyzed uniformly. We also describe a number of updates to our methodology, including updated helium emissivities. Enabled by the large, high-quality dataset, we examine our sample targets for potential systematic errors, which could bias their results. We perform a standard 95% confidence level χ2 cut and find that a significantly larger fraction (47/54 = 87%) of our sample qualifies than for previous datasets. We also screen for quality and reliability, flagging targets which may introduce significant systematic errors, producing a dataset of 41 targets. In a significant breakthrough for the field, that dataset includes 15 high SNR targets with low metallicity (O/H < 4 × 10-5). Due to this low-metallicity dataset, for the first time, a weighted average for determining the primordial helium abundance (Yp) is well-justified and produces a robust result. By weighted average of our 15 low-metallicity targets, we determine Yp = 0.2458 ± 0.0013. This result achieves an unprecedented precision of 0.5%, and it is in good agreement with the BBN result, Yp = 0.2467 ± 0.0002, based on the Planck determination of the baryon density.