The open cluster NGC 2345: a study of chemical abundances with near-infrared IGRINS high-resolution spectra

• Published in: Monthly notices of the Royal Astronomical Society 2024-01, Vol.527 (1), p.1389-1404
• Main Authors: Holanda, N, Roriz, M P, Drake, N A, Junqueira, S, Daflon, S, da Silva, J R P, Pereira, C B
• Format: Article
• Language: English
• Subjects: Abundance; Aluminum; Astronomical models; Carbon 12; Galactic clusters; Gratings (spectra); Infrared analysis; Infrared spectra; Infrared spectroscopy; Infrared stars; Isotope ratios; Magnesium; Metallicity; Near infrared radiation; Nuclear fusion; Open clusters; Resolution; Signal to noise ratio; Spectrum analysis
• ISSN: 0035-8711; 1365-2966
• DOI: 10.1093/mnras/stad3280

ABSTRACT Open clusters are relatively young and numerous. These systems are distributed throughout the Galactic disc and provide insights on the chemistry of the Milky Way. In this study, we provide a near-infrared spectroscopic analysis of four stars of the young open cluster NGC 2345. Our infrared data present a resolving power of R ≈ 45 000, covering the H- and K-bands (1.5–2.5 μm), and high-signal-to-noise ratio, which are gathered with the Immersion Grating Infrared Spectrograph (IGRINS) at the Gemini Observatory. From atmospheric parameters previously derived via optical spectroscopy, we obtain abundances for C (12C16O), N (12C14N), O (16OH), F (H19F), Na, Mg, Al, Si, P, S, K, Ca, Sc, Ti, Cr, Fe, Ni, Ce, Nd, and Yb. Additionally, the 12C/13C (13C16O), 16O/17O (12C17O), and 16O/18O (12C18O) isotopic ratios are obtained. We compare the infrared results with a previous work based on optical spectral analysis, but chemical species such as F, S, P, K, and Yb are determined for the first time in stars of NGC 2345. We also confirm a low metallicity ([Fe/H]  =  −0.32 ± 0.04) and slight enrichment in s-process elements, as already noticed in works available in the literature, but we do not find any enrichment in F. Our results demonstrate excellent agreement between our measured isotopic ratios 12C/13C and 16C/17O and models of stellar nucleosynthesis, while we find that the abundance of 18O is overestimated in comparison to our measurements. Finally, we assess our findings in comparison to the chemical patterns observed in open clusters, classified by both their age and Galactocentric distances, and highlight the need for a more comprehensive sample of young clusters within the 9–11 kpc range for a proper comparison.