{
  "id": "1505.06597",
  "version": "v1",
  "published": "2015-05-25T11:33:08.000Z",
  "updated": "2015-05-25T11:33:08.000Z",
  "title": "The Carina Project. VIII. On the α-element abundances",
  "authors": [
    "M. Fabrizio",
    "M. Nonino",
    "G. Bono",
    "F. Primas",
    "F. Thévenin",
    "P. B. Stetson",
    "S. Cassisi",
    "R. Buonanno",
    "G. Coppola",
    "R. O. da Silva",
    "M. Dall'Ora",
    "I. Ferraro",
    "K. Genovali",
    "R. Gilmozzi",
    "G. Iannicola",
    "M. Marconi",
    "M. Monelli",
    "M. Romaniello",
    "A. R. Walker"
  ],
  "comment": "21 pages, 19 figures, 11 tables, accepted for publication in A&A",
  "categories": [
    "astro-ph.GA"
  ],
  "abstract": "We have performed a new abundance analysis of Carina Red Giant (RG) stars from spectroscopic data collected with UVES (high resolution) and FLAMES/GIRAFFE (high and medium resolution) at ESO/VLT. The former sample includes 44 RGs, while the latter consists of 65 (high) and ~800 (medium resolution) RGs, covering a significant fraction of the galaxy's RG branch (RGB), and red clump stars. To improve the abundance analysis at the faint magnitude limit, the FLAMES/GIRAFFE data were divided into ten surface gravity and effective temperature bins. The spectra of the stars belonging to the same gravity/temperature bin were stacked. This approach allowed us to increase by at least a factor of five the signal-to-noise ratio in the faint limit (V>20.5mag). We took advantage of the new photometry index cU,B,I introduced by Monelli et al. (2014), as an age and probably a metallicity indicator, to split stars along the RGB. These two stellar populations display distinct [Fe/H] and [Mg/H] distributions: their mean Fe abundances are -2.15$\\pm$0.06dex (sig=0.28), and -1.75$\\pm$0.03dex (sig=0.21), respectively. The two iron distributions differ at the 75% level. This supports preliminary results by Lemasle et al. (2012) and by Monelli et al. (2014). Moreover, we found that the old and intermediate-age stellar populations have mean [Mg/H] abundances of -1.91$\\pm$0.05dex (sig=0.22) and -1.35$\\pm$0.03dex (sig=0.22); these differ at the 83% level. Carina's {\\alpha}-element abundances agree, within 1sigma, with similar abundances for field Halo stars and for cluster (Galactic, Magellanic) stars. The same outcome applies to nearby dwarf spheroidals and ultra-faint dwarf galaxies, in the iron range covered by Carina stars. Finally, we found evidence of a clear correlation between Na and O abundances, thus suggesting that Carina's chemical enrichment history is quite different than in the globular clusters.",
  "revisions": [
    {
      "version": "v1",
      "updated": "2015-05-25T11:33:08.000Z"
    }
  ],
  "analyses": {
    "keywords": [
      "carina project",
      "abundance analysis",
      "stellar populations display distinct",
      "medium resolution",
      "mean fe abundances"
    ],
    "note": {
      "typesetting": "TeX",
      "pages": 21,
      "language": "en",
      "license": "arXiv",
      "status": "editable"
    }
  }
}