A Unified Exploration of the Chronology of the Galaxy

Abstract

The Milky Way has distinct structural stellar components linked to its formation and subsequent evolution, but disentangling them is nontrivial. With the recent availability of high-quality data for a large numbers of stars in the Milky Way, it is a natural next step for research in the evolution of the Galaxy to perform automated explorations with unsupervised methods of the structures hidden in the combination of large-scale spectroscopic, astrometric, and asteroseismic data sets. We determine precise stellar properties for 21,076 red giants, mainly spanning 2-15 kpc in Galactocentric radii, making it the largest sample of red giants with measured asteroseismic ages available to date. We explore the nature of different stellar structures in the Galactic disc by using Gaussian mixture models as an unsupervised clustering method to find substructure in the combined chemical, kinematic, and age subspace. The best-fit mixture model yields four distinct physical Galactic components in the stellar disc: the thin disc, the kinematically heated thin disc, the thick disc, and the stellar halo. We find hints of an age asymmetry between the Northern and Southern hemisphere and we measure the vertical and radial age gradient of the Galactic disc using the asteroseismic ages extended to further distances than previous studies.

18 pages, 12 figures, accepted for publication in MNRAS

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Cited by in corpus (6)

• The APO-K2 Catalog. II. Accurate Stellar Ages for Red Giant Branch Stars across the Milky Way
• Asteroseismic Study of Subgiants and Giants of the Open Cluster M67 using Kepler/K2: Expanded Sample and Precise Masses
• Exploring the dependence of chemical traits on metallicity: chemical trends for red giant stars with asteroseismic ages
• zoomies: A tool to infer stellar age from vertical action in Gaia data
• Asteroseismically Inferred Ages of 132,000 Red Giants with TESS
• Dissecting stellar populations with manifold learning I. Validation of the method on a synthetic Milky Way-like galaxy