Fluorine Abundances in the Globular Cluster M 4

We present chemical abundances for the elements carbon, sodium, and fluorine in 15 red giants of the globular cluster M 4, as well as six red giants of the globular cluster $\omega$ Centauri. The chemical abundances were calculated in LTE via spectral synthesis. The spectra analyzed are high-resolution spectra obtained in the near-infrared region around $\lambda$2.3$\mu$m with the Phoenix spectrograph on the 8.1m Gemini South Telescope, the IGRINS spectrograph on the McDonald Observatory 2.7m Telescope, and the CRIRES spectrograph on the ESO 8.2m Very Large Telescope. The results indicate a significant reduction in the fluorine abundances when compared to previous values from the literature for M 4 and $\omega$ Centauri, due to a downward revision in the excitation potentials of the HF(1-0) R9 line used in the analysis. The fluorine abundances obtained for the M 4 red giants are found to be anti-correlated with those of Na, following the typical pattern of abundance variations seen in globular clusters between distinct stellar populations. In M 4, as the Na abundance increases by $\sim$+0.4 dex, the F abundance decreases by $\sim$-0.2 dex. A comparison with abundance predictions from two sets of stellar evolution models finds that the models predict somewhat less F depletion ($\sim$-0.1 dex) for the same increase of +0.4 dex in Na

Ages and metallicities of stellar clusters using S-PLUS narrow-band integrated photometry: the Small Magellanic Cloud

The Magellanic Clouds are the most massive and closest satellite galaxies of the Milky Way, with stars covering ages from a few Myr up to 13 Gyr. This makes them important for validating integrated light methods to study stellar populations and star-formation processes, which can be applied to more distant galaxies. We characterized a set of stellar clusters in the Small Magellanic Cloud (SMC), using the $\textit{Southern Photometric Local Universe Survey}$. This is the first age (metallicity) determination for 11 (65) clusters of this sample. Through its 7 narrow bands, centered on important spectral features, and 5 broad bands, we can retrieve detailed information about stellar populations. We obtained ages and metallicities for all stellar clusters using the Bayesian spectral energy distribution fitting code $\texttt{BAGPIPES}$. With a sample of clusters in the color range $-0.20 < r-z < +0.35$, for which our determined parameters are most reliable, we modeled the age-metallicity relation of SMC. At any given age, the metallicities of SMC clusters are lower than those of both the Gaia Sausage-Enceladus disrupted dwarf galaxy and the Milky Way. In comparison with literature values, differences are $\Delta$log(age)$\approx0.31$ and $\Delta$[Fe/H]$\approx0.41$, which is comparable to low-resolution spectroscopy of individual stars. Finally, we confirm a previously known gradient, with younger clusters in the center and older ones preferentially located in the outermost regions. On the other hand, we found no evidence of a significant metallicity gradient.Comment: 12 pages, 11 figure

Metallicity determination in open star clusters by exploring Gaia—J-PLUS synergy

Under various initial conditions, open star clusters serve as valuable laboratories for studying stellar evolution and its outcomes. The Gaia mission has significantly advanced our understanding of the Milky Way through precise astrometric data, while the Javalambre-Photometric Local Universe Survey (J-PLUS) offers extensive multiband photometric information. In this study, we investigate a list of 24 open star clusters, including 13 recently discovered ones, by combining the precise astrometric measurements from Gaia with data from J-PLUS. By utilizing machine learning algorithms, we trained models using Gaia and J-PLUS data to determine atmospheric parameters for members individually, in particular yielding metallicities estimates for these clusters. Importantly, this methodology can be readily extended to other multiband photometric surveys, providing a direct pathway to explore the metallicity properties of other various clusters

Fluorine Abundances in the Galactic Nuclear Star Cluster

International audienceAbundances 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 ( = +0.08 ± 0.04), with a slight enhancement of the F/Fe abundance ratio ( = +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

Fluorine Abundances in the Galactic Disk

The chemical evolution of fluorine is investigated in a sample of Milky Way red giant stars that span a significant range in metallicity from [Fe/H] ∼-1.3 to 0.0 dex. Fluorine abundances are derived from vibration-rotation lines of HF in high-resolution infrared spectra near 2.335 μm. The red giants are members of the thin and thick disk/halo, with two stars being likely members of the outer disk Monoceros overdensity. At lower metallicities, with [Fe/H] <-0.4 to-0.5, the abundance of F varies as a primary element with respect to the Fe abundance, with a constant subsolar value of [F/Fe] ∼-0.3 to-0.4 dex. At larger metallicities, however, [F/Fe] increases rapidly with [Fe/H] and displays a near-secondary behavior with respect to Fe. Comparisons with various models of chemical evolution suggest that in the low-metallicity regime (dominated here by thick-disk stars), a primary evolution of 19F with Fe, with a subsolar [F/Fe] value that roughly matches the observed plateau, can be reproduced by a model incorporating neutrino nucleosynthesis in the aftermath of the core collapse in Type II supernovae. A primary behavior for [F/Fe] at low metallicity is also observed for a model including rapidly rotating low-metallicity massive stars, but this overproduces [F/Fe] at low metallicity. The thick-disk red giants in our sample span a large range of galactocentric distance (R g ∼ 6-13.7 kpc) yet display a roughly constant value of [F/Fe], indicating a very flat gradient (with a slope of 0.02 ± 0.03 dex kpc-1) of this elemental ratio over a significant portion of the Galaxy havin

Evidence of deep mixing in IRS 7, a cool massive supergiant member of the Galactic nuclear star cluster

International audienceThe centre of the Milky Way contains stellar populations spanning a range in age and metallicity, with a recent star formation burst producing young and massive stars. Chemical abundances in the most luminous stellar member of the nuclear star cluster (NSC), IRS 7, are presented for 19F, 12C, 13C, 14N, 16O, 17O, and Fe from a local thermodynamic equilibrium analysis based on spherical modelling and radiative transfer with a 25-M⊙ model atmosphere, whose chemistry was tailored to the derived photospheric abundances. We find IRS 7 to be depleted heavily in both 12C (~-0.8 dex) and 16O (~-0.4 dex), while exhibiting an extremely enhanced 14N abundance (~+1.1 dex), which are isotopic signatures of the deep mixing of CNO-cycled material to the stellar surface. The 19F abundance is also heavily depleted by ~1 dex relative to the baseline fluorine of the NSC, providing evidence that fluorine along with carbon constrain the nature of the deep mixing in this very luminous supergiant. The abundances of the minor isotopes 13C and 17O are also derived, with ratios of 12C/13C ~ 5.3 and 16O/17O ~ 525. The derived abundances for IRS 7, in conjunction with previous abundance results for massive stars in the NSC, are compared with rotating and non-rotating models of massive stars and it is found that the IRS 7 abundances overall follow the behaviour predicted by stellar models. The depleted fluorine abundance in IRS 7 illustrates, for the first time, the potential of using the 19F abundance as a mixing probe in luminous red giants