MgAl burning chain in Omega Centauri

Abstract

In this study, we report the results of Fe, Mg, Al, and Si abundances analysis for a sample of 439 stars in Omega Centauri, using high-resolution spectra obtained with the VLT/FLAMES multi-object spectrograph. Our analysis reveals the presence of four distinct Fe populations, with the main peak occurring at low metallicity, consistent with previous literature findings. We observe a discrete and pronounced Mg-Al anti-correlation, which exhibits variations in shape and extension as a function of metallicity. Specifically, this anti-correlation is present in stars with metallicities lower than approximately -1.3 dex, while it becomes less evident or absent for higher [Fe/H] values. Additionally, we detect (anti-) correlations between Mg and Si, and between Al and Si, whose extensions also vary with metallicity, similar to the Mg-Al anti-correlation. These results suggest that the MgAl cycle plays a crucial role in the formation of multiple populations in Omega Centauri, with the presence of all (anti-) correlations at metallicities lower than -1.3 dex providing evidence for the burning of Mg at very high temperatures (> 10^8 K), at least in the metal-poor regime. Furthermore, we observe a clear trend of stars with [Al/Fe] > +0.5 dex as a function of metallicity, confirming for the first time the existence of the two channels of Al production and destruction. This evidence can help to provide further constraints on the potential nature of the polluters responsible for the observed chemical anomalies in this stellar system. Finally, we find that the two most metal-poor populations identified in our sample are compatible with null or very small metallicity dispersion and we discuss how this result fit into a scenario where Omega Centauri is the remnant of a disrupted nucleated dwarf galaxy.

Accepted for pubblication in A&A

References in corpus (20)

• The Gaia mission
• What is a globular cluster? An observational perspective
• DAOSPEC: an automatic code for measuring equivalent widths in high-resolution stellar spectra
• The nucleus of the Sagittarius dSph galaxy and M54: a window on the process of galaxy nucleation
• Light nuclei in galactic globular clusters : constraints on the self-enrichment scenario from nucleosynthesis
• Exploring Anticorrelations and Light Element Variations in Northern Globular Clusters Observed by the APOGEE Survey
• Exploiting the Gaia EDR3 photometry to derive stellar temperatures
• A homogeneous analysis of globular clusters from the APOGEE survey with the BACCHUS code. I. The Northern clusters
• Reconstructing the Disrupted Dwarf Galaxy $Gaia$-Sausage/Enceladus Using its Stars and Globular Clusters
• The metallicity spread and the age-metallicity relation of Omega Centauri
• Chemical abundances in the nucleus of the Sagittarius dwarf spheroidal galaxy
• A deep view into the nucleus of the Sagittarius Dwarf Spheroidal Galaxy with MUSE. I. Data and stellar population characterization
• Revisiting nucleosynthesis in globular clusters: the case of NGC 2808 and the role of He and K
• Evidence of AGB pollution in Galactic globular clusters from the Mg-Al anticorrelations observed by the APOGEE survey
• A homogeneous comparison between the chemical composition of the Large Magellanic Cloud and the Sagittarius dwarf galaxy
• Peeking beneath the precision floor I: metallicity spreads and multiple elemental dispersions in the globular clusters NGC 288 and NGC 362
• The Mg-K anti-correlation in Omega Centauri
• Multiple Stellar Populations of Globular Clusters From Homogeneous Ca-CN-CH-NH Photometry. VII. Metal-Poor Populations in 47 Tucanae (NGC 104)
• A new formation model for omega Centauri: the crossroad of astrophysical processes
• M92 (NGC~6341) Is a Metal-Complex Globular Cluster with an Atypical Primordial Population

Cited by in corpus (9)

• oMEGACat III. Multi-band photometry and metallicities reveal spatially well-mixed populations within $\omega$ Centauri's half-light radius
• Abundance ties: Nephele and the globular cluster population accreted with $\omega$ Cen. Based on APOGEE DR17 and Gaia EDR3
• The Bulge Cluster Origin (BulCO) survey at the ESO-VLT: probing the early history of the Milky Way assembling. Design and first results in Liller1
• Studying stellar populations in Omega Centauri with phylogenetics
• Kinematics of metallicity populations in Omega Centauri using Gaia Focused Product Release and Hubble Space Telescope
• Studying Binary Systems in Omega Centauri with MUSE. I. Detection of Spectroscopic Binaries
• Chemical tagging with APOGEE, MUSE, and HST: constraints on the formation of $\omega$ Centauri
• Noble gases Neon and argon: a role for the chemical patterns of multiple populations in globular clusters?
• Disruption of a Giant: Spectroscopic Identification of Members in the Periphery and Tidal Tails of $\omega$ Centauri