SDSS-V LVM: Mapping of plasma temperatures in the Lagoon Nebula reveals the origin of long-standing chemical abundance discrepancies
Authors: Amrita Singh, Guillermo A. Blanc, Kathryn Kreckel, J. E. Méndez-Delgado, Christophe Morisset, Sebastián F. Sánchez, Oleg Egorov, Niv Drory, Nimisha Kumari, Fu-Heng Liang, Enrico Congiu, Alfredo Mejía-Narváez, Evelyn J. Johnston, José G. Fernández-Trincado, Hemanth Bommireddy, Abhinna Sundar Samantaray, Thomas Hilder, Rodolfo de J. Zermeño, Ivan Katkov, Dhanesh Krishnarao, Juna A. Kollmeier
Abstract
Knowing the chemical composition of interstellar gas is essential for understanding the chemical evolution of galaxies. Ionized nebulae provide key laboratories for this purpose, where chemical abundances are commonly derived from emission lines of heavy ions such as doubly ionized oxygen, $O^{++}$. Abundances can be inferred either from collisionally excited lines (CELs) or from recombination lines (RLs). However, for more than 80 years, the former have yielded systematically lower abundances than the latter. We map this ''abundance discrepancy'' using the first spatially resolved integral field unit (IFU) observations of $O^{++}$ RLs and CELs across a Milky Way H II region: the Lagoon Nebula (a.k.a. M8). Modeling the data using a plasma temperature perturbation model, we present unequivocal evidence that electron temperature ($T_e$) fluctuations drive the abundance discrepancy in M8. We find a tight correlation between the abundance discrepancy and the difference between $T_e$ derived from the classical CEL method and a hybrid RL/CEL approach. We identify this Te discrepancy as an observational proxy for the amplitude of the thermal fluctuations, providing a new, direct way to quantify their effect on nebular abundances. The correlation constrains the mean electron temperature of the gas. Adopting this mean temperature reconciles CEL and RL abundances, effectively eliminating the abundance discrepancy.
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Abstract
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Abstract
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Abstract
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Abstract
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Abstract
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Abstract
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Abstract
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Abstract
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Prior work it builds on
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Chemical evolution of galaxiesG. Shields · 2000 · Revista Mexicana De Astronomia Y Astrofisica · cited 138 times · Not summarized yet
Chemical evolution of galaxies reviews how chemical abundances and ionized nebulae inform understanding of galaxy evolution.
Abstract
Resumen en: Chemical abundances provide important clues to the evolution of galaxies. Ionized nebulae are one of the main sources of chemical abundance measurements...
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Astrophysics of Gaseous Nebulae and Active Galactic NucleiD. Osterbrock, G. Ferland · 1989 · cited 6,963 times · Not summarized yet
Astrophysics of Gaseous Nebulae and Active Galactic Nuclei provides foundational coverage of gaseous nebula physics relevant to emission-line temperature and abundance diagnostics.
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