Abstract
| Méndez Delgado |
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| Metals in the Universe could be much more abundant than we thought |
| HII regions exhibit a wealth of emission lines that are the fundamental basis for estimating the chemical composition of the Universe. Metallic abundances are particularly important because they are essential to the understanding of several phenomena such as nucleosynthesis, star formation and chemical evolution. For more than 80 years, however, a discrepancy of a factor of around two between metallic abundances derived with collisional excited lines (CELs) and recombination lines (RLs) has thrown our absolute abundance determinations into doubt. The widely observed CELs are ~10,000 times brighter than RLs but exponentially dependent on the nebular temperature. Which of the indicators (if any) gives the correct metallicity? We show that all the available spectra of the literature with simultaneous detections of heavy elements RLs and CELs indicate the presence of temperature inhomogeneities within the highly ionized gas, causing the longstanding abundance discrepancy problem by introducing systematic underestimations of the metallicities based on CELs. Our work implies that most nebular metallicity determinations, those based on CELs, must be revised as they may be severely underestimated. The evidence suggest that this effect could be greater in regions of lower metallicity, such as the JWST high-z galaxies. Fortunately, it is possible to correctly determine metallicities using CELs of low degree of ionization ions, following our proposed empirical relations |