Séminaire/Seminar Galaxies |
| « Understanding the accretion history of our Galaxy through the lens of globular clusters » |
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Giulia Pagnini |
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In the context of the hierarchical formation of galaxies, the search for galaxies accreted by the Milky Way has been a subject of study for decades. The main focus of this research is on Galactic globular clusters, ancient stellar systems that are now distributed mainly in the halo of the Milky Way. Because of their age and their location in the part of the Galaxy most exposed to accretion from other galaxies, globular clusters are currently being intensely studied to determine their origin: whether they originated within the Milky Way or were accreted over time from other galaxies. Traditionally, identifying stars and globular clusters with a common galactic progenitor involves studying integrals of motion spaces such as orbital energy and angular momentum, assuming that these quantities remain conserved during interactions. In this talk, I will first present the results of the analysis of a set of N-body simulations that simulate the accretion of one or two satellites, along with their globular cluster populations, onto a Milky Way-like galaxy. Contrary to conventional assumptions in the literature, this analysis shows that accreted globular clusters do not cluster in integrals of motion spaces. Furthermore, it suggests a significant overlap between accreted globular clusters and dynamically heated globular clusters originally born in situ. Motivated by these results, in the second part of the talk I propose a new approach based on the search for common chemical properties among Galactic globular clusters. In particular, I focus on the identification of Galactic globular clusters that are chemically similar to ? Centauri (NGC 5139), a peculiar cluster that is thought to be the remnant of an ancient satellite galaxy accreted by the Milky Way, potentially introducing its own globular cluster system. To this end, I applied a Gaussian Mixture Model approach using a multi-dimensional chemical abundance dataset provided by APOGEE DR17 measurements. Beyond ? Centauri itself, this analysis pinpoints six globular clusters that have a significant fraction of stars compatible with ? Centauri that may have been introduced into the Milky Way by ? Centauri's progenitor galaxy, named Nephele. These results open up the possibility of using the same approach, based on chemical properties, to identify Nephele field stars that have been dispersed into the Milky Way field due to tidal forces.
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jeudi 12 décembre 2024 - 11:30 Salle des séminaires Évry Schatzman Institut d'Astrophysique de Paris |
| Page web du séminaire / Seminar's webpage |