{
  "id": "2406.18636",
  "version": "v1",
  "published": "2024-06-26T18:00:00.000Z",
  "updated": "2024-06-26T18:00:00.000Z",
  "title": "The Pristine Inner Galaxy Survey (PIGS) X. Probing the early chemical evolution of the Sagittarius dwarf galaxy with carbon abundances",
  "authors": [
    "Federico Sestito",
    "Anke Ardern-Arentsen",
    "Sara Vitali",
    "Martin Montelius",
    "Romain Lucchesi",
    "Kim A. Venn",
    "Nicolas F. Martin",
    "Julio F. Navarro",
    "Else Starkenburg"
  ],
  "comment": "Submitted to A&A. 8 Figures. The abstract in the metadata is a shorter version than the actual one",
  "categories": [
    "astro-ph.GA",
    "astro-ph.SR"
  ],
  "abstract": "Carbon abundances, especially at low metallicity, reveal the early chemical evolution of a system, tracing the supernovae (SNe) that contributed and how much of their ejecta made it into the next stellar generation. Our sample from the \\textit{Pristine} Inner Galaxy Survey (PIGS) includes $\\sim 350$ metal-poor ([Fe/H]~$<-1.5$) stars in the main body of Sgr with good quality spectroscopic observations. Our metal-poor Sgr population has a larger velocity dispersion than metal-rich Sgr from the literature, which could be explained by outside-in star formation, extreme Galactic tidal perturbations and/or the presence of a metal-rich disc/bar $+$ a metal-poor halo. The average carbon abundance in Sgr is similar to that of other classical dwarf galaxies (DGs) and consistently lower than in the Milky Way by $\\sim0.2-0.3$~dex at low metallicity. The interstellar medium in DGs, including Sgr, may have retained yields from more energetic Pop III and II SNe, thereby reducing the average [C/Fe]. Additionally, SNe~Ia, producing more Fe than C, would start to contribute at lower metallicity in DGs/Sgr than in the Galaxy. The presence of a [C/Fe] gradient for Sgr stars with [Fe/H]~$\\gtrsim-2.0$ ($\\sim 6.8\\times 10^{-4}$ dex arcmin$^{-1}$) suggests that SNe~Ia contributed in the system at those metallicities, especially in its inner regions. There is a low frequency of carbon-enhanced metal-poor (CEMP) stars in our Sgr sample. At higher metallicity/carbon abundance (mostly CEMP-s) this may be due to photometric selection effects, but those are less likely to affect CEMP-no stars. We propose that, given the lower average [C/Fe] in DGs, using the same CEMP definition ([C/Fe]~$>+0.7$) as in the Galaxy under-predicts the number of CEMP stars in DGs, and for Sgr a cut at [C/Fe]$~\\sim +0.35$ may be more appropriate, which brings the frequency of CEMP stars in agreement with that in the Galaxy.",
  "revisions": [
    {
      "version": "v1",
      "updated": "2024-06-26T18:00:00.000Z"
    }
  ],
  "analyses": {
    "keywords": [
      "pristine inner galaxy survey",
      "early chemical evolution",
      "carbon abundance",
      "sagittarius dwarf galaxy",
      "low metallicity"
    ],
    "note": {
      "typesetting": "TeX",
      "pages": 0,
      "language": "en",
      "license": "arXiv",
      "status": "editable"
    }
  }
}