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The Andromeda Galaxy’s Last Major Merger: Constraints from the survey of Planetary Nebulae
Published online by Cambridge University Press: 13 February 2024
Abstract
The Andromeda galaxy (M 31) has experienced a tumultuous merger history as evidenced by the many substructures present in its inner halo. We use planetary nebulae (PNe) as chemodynamic tracers to shed light on the recent merger history of M 31. We identify the older dynamically hotter thicker disc in M 31 and a distinct younger dynamically colder thin disc. The two discs are also chemically distinct with the PN chemodynamics implying their formation in a ‘wet’ major merger (mass ratio ∼ 1:5) ∼ 2.5–4.5 Gyr ago. From comparison of PN line-of-sight velocities in the inner halo substructures with predictions of a major-merger model in M 31, we find that the same merger event that formed the M 31 thick and thin disc is also responsible for forming these substructures. We thereby obtain constraints on the recent formation history of M 31 and the properties of its cannibalized satellite.
Keywords
- Type
- Contributed Paper
- Information
- Proceedings of the International Astronomical Union , Volume 18 , Symposium S377: Early Disk-Galaxy Formation from JWST to the Milky Way , December 2022 , pp. 123 - 126
- Copyright
- © The Author(s), 2024. Published by Cambridge University Press on behalf of International Astronomical Union