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Dead man tells tales: metallicity distribution of the Milky Way stellar halo reveals the past of the GSE progenitor galaxy

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arxiv 2310.05287 v1 pith:TU5L7YTE submitted 2023-10-08 astro-ph.GA

classification astro-ph.GA
keywords galaxygradientmetallicityprogenitorradialaccretedapproxhalo
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abstract

The Gaia-Sausage-Enceladus~(GSE) stands out as the largest known ancient accretion event in the Milky Way~(MW) history. Despite this significance, the parameters of its progenitor galaxy are still poorly constrained. We identify GSE stars from the APOGEE DR17 using Gaussian mixture models and recover a negative radial metallicity gradient for the GSE debris within the MW stellar halo, with a magnitude of $\approx -0.014^{-0.002}_{-0.022}$ dex/kpc. We argue that this gradient reflects the radial metallicity gradient of the GSE galaxy progenitor before it was disrupted by the MW. By investigating the cosmological HESTIA simulations and $N$-body models of galaxy mergers, we constrain the radial metallicity gradient of the GSE-progenitor to be $\approx -0.1^{-0.06}_{-0.15}$ dex/kpc. We, therefore, propose that a chemical tagging of accreted stars using their integrals of motion, although they are not conserved during mergers, provide essential information about the structure and the past of systems accreted onto the MW.

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Forward citations

Cited by 5 Pith papers

Reviewed papers in the Pith corpus that reference this work. Sorted by Pith novelty score. Full citation record

  1. The chemodynamical memory of a major merger in a NIHAO-UHD Milky Way analogue -- II. Were Splash stars heated or already born hot?

    astro-ph.GA 2025-10 conditional novelty 6.0 of 10

    In a NIHAO-UHD Milky Way analogue, Splash-like stars were already born on dynamically hot orbits; the last major merger did not significantly heat them.

  2. Chemical decoding of kinematic substructures in the Galactic halo

    astro-ph.GA 2025-09 conditional novelty 6.0 of 10

    Chemical tagging via Gaussian Mixture Model on multiple abundances shows that halo substructures Sequoia, Heracles, Thamnos, and Helmi Stream are contaminated mixtures dominated by GSE and disc stars, with additional ...

  3. Rediscovering the Milky Way with orbit superposition approach and APOGEE data II. Chrono-chemo-kinematics of the disc

    astro-ph.GA 2024-11 conditional novelty 6.0 of 10

    Orbit superposition of APOGEE stars yields a mass-weighted Milky Way disc map showing a less prominent alpha-bimodality and two distinct inner and outer age-metallicity sequences.

  4. Rediscovering the Milky Way with orbit superposition approach and APOGEE data III. Panoramic view of the bulge

    astro-ph.GA 2024-11 conditional novelty 5.0 of 10

    A model-dependent orbit superposition reconstruction of APOGEE bulge stars finds the bulge is a 4:3 mix of thick and thin disc populations and is metal-rich relative to the surrounding disc when viewed in 3D.

  5. Nearby stellar substructures in the Galactic halo from DESI Milky Way Survey Year 1 Data Release

    astro-ph.GA 2025-04 conditional novelty 4.0 of 10

    Five known nearby halo substructures are re-detected with HDBSCAN* clustering in DESI Year 1 data, and DESI metallicities confirm three of them as chemically distinct.

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