2022ApJ...929...24G

Abundances of fluorine (¹⁹F), as well as isotopic ratios of ¹⁶O/¹⁷O, are derived in a sample of luminous young (∼10⁷-10⁸ yr) red giants in the Galactic center (with galactocentric distances ranging from 0.6-30 pc), using high-resolution infrared spectra and vibration-rotation lines of H¹⁹F near λ2.3 µm. Five of the six red giants are members of the Nuclear star cluster that orbits the central supermassive black hole. Previous investigations of the chemical evolution of ¹⁹F in Galactic thin and thick-disk stars have revealed that the nucleosynthetic origins of ¹⁹F may be rather complex, resulting from two, or more, astrophysical sites; fluorine abundances behave as a primary element with respect to Fe abundances for thick-disk stars and as a secondary element in thin-disk stars. The Galactic center red giants analyzed fall within the thin-disk relation of F with Fe, having near-solar, to slightly larger, abundances of Fe (<[Fe/H]> = +0.08 ± 0.04), with a slight enhancement of the F/Fe abundance ratio (<[F/Fe]> = +0.28 ± 0.17). In terms of their F and Fe abundances, the Galactic center stars follow the thin-disk population, which requires an efficient source of ¹⁹F that could be the winds from core-He burning Wolf-Rayet stars, or thermally pulsing AGB stars, or a combination of both. The observed increase of [F/Fe] with increasing [Fe/H] found in thin-disk and Galactic center stars is not predicted by any published chemical evolution models that are discussed, thus a quantitative understanding of yields from the various possible sources of ¹⁹F remains unknown.