{
  "id": "2405.00315",
  "version": "v1",
  "published": "2024-05-01T04:34:53.000Z",
  "updated": "2024-05-01T04:34:53.000Z",
  "title": "At the same age, metallicity, and alpha-enhancement, sodium is a more effective tracer of the young and old sequences of the Milky Way disc",
  "authors": [
    "Evans K. Owusu",
    "Sven Buder",
    "Ashley J. Ruiter",
    "Ivo R. Seitenzahl",
    "Nicolás Rodríguez-Segovia"
  ],
  "comment": "13 pages, 8 figures, submitted to PASA, comments welcome",
  "categories": [
    "astro-ph.GA",
    "astro-ph.SR"
  ],
  "abstract": "Trends in the enrichment of elements with stellar ages are a powerful avenue to identify unexplained origins of the elements. We investigate the stellar abundance trends of low to intermediate-mass stars using the GALAH DR3 high-resolution spectroscopic dataset of 6234 solar-type stars. Our study explores the elemental abundance [X/Fe] of sodium (Na) with age. We find a pronounced enrichment in [Na/Fe] at super solar metallicity (i.e., [Fe/H] above 0) in the old sequence of Milky Way disc stars, a trend demanding a deeper understanding of the underlying source(s) responsible for the nucleosynthesis. This progressive [Na/Fe] enrichment at the young end of the old sequence has essential implications for Galactic archaeology. In this work, we propose a novel selection technique for separating the Milky Way's thick and thin disc stellar populations (i.e., old and young sequences) based on the observed [Na/Fe] rise of roughly 0.1 dex for stars around 5 - 8 Gyr old. We also compare our selection method to the conventional [Mg/Fe] vs [Fe/H] selection approach, and we find that our new Na-based selection method better disentangles the overlap between young- and old-sequence disc stars at these intermediate ages. This is especially true at super solar [Fe/H], where [Mg/Fe] vs [Fe/H] or [alpha/Fe] vs [Fe/H] separation approaches exhibit a lot of overlap. This new selection method should help us better understand the Milky Way disc's formation history.",
  "revisions": [
    {
      "version": "v1",
      "updated": "2024-05-01T04:34:53.000Z"
    }
  ],
  "analyses": {
    "keywords": [
      "milky way disc",
      "old sequence",
      "selection method better disentangles",
      "dr3 high-resolution spectroscopic dataset",
      "way discs formation history"
    ],
    "note": {
      "typesetting": "TeX",
      "pages": 13,
      "language": "en",
      "license": "arXiv",
      "status": "editable"
    }
  }
}