{
  "id": "astro-ph/0312628",
  "version": "v1",
  "published": "2003-12-27T22:20:52.000Z",
  "updated": "2003-12-27T22:20:52.000Z",
  "title": "Composition of the Galactic bulge",
  "authors": [
    "Andrew McWilliam",
    "R. Michael Rich"
  ],
  "comment": "contributed paper to Carnegie Observatories Astrophysics Series, Volume 4: Origin and Evolution of the Elements, A.McWilliam and M. Rauch (eds.) http://www.ociw.edu/symposia/symposium4/proceedings.html",
  "categories": [
    "astro-ph"
  ],
  "abstract": "We present detailed abundance results for 9 Galactic bulge stars in Baade's Window, based on HIRES (R=45,000--60,000) spectra taken with the Keck I telescope. The alpha elements show non-uniform enhancements relative to the Solar neighborhood trends: Mg and Si are enhanced in all our bulge stars by $\\sim$0.5--0.3 dex, showing a slight decrease with increasing [Fe/H]. Oxygen is enhanced in most bulge stars, similar to the Galactic halo, but the [O/Fe] ratios suddenly decline beginning at [Fe/H]=$-$0.5 dex, with a slope consistent with no oxygen production in the bulge for [Fe/H]$\\geq$$-$0.5 dex. The observed production of magnesium in the absence of oxygen synthesis appears to be inconsistent with current predictions for supernova nucleosynthesis yields; we suggest that this may be connected to the Wolf-Rayet phenomenon, which occurs in the pertinent metallicity range. The trend of [Ti/Fe] shows an enhancement relative to the solar neighborhood of $\\sim$0.3 dex, but declines somewhat by solar metallicity; thus, the Ti trend is less extreme than found by McWilliam & Rich (1994, MR94). For metal-poor bulge stars calcium is enhanced by $\\sim$0.3 dex, similar to the Galactic halo, but in our bulge stars with [Fe/H]$\\geq$$-$0.5, Ca show a slight deficiency relative to the solar neighborhood value, consistent with the findings of MR94; this may indicate a slightly top-heavy IMF as suggested by MR94 and McWilliam (1997). Aluminum is enhanced in all our Galactic bulge giant stars by $\\sim$0.25 dex; we argue that this is consistent with nucleosynthesis dominated by type II supernova events (SNII), implied by the Mg and Si enhancements. (Abridged)",
  "revisions": [
    {
      "version": "v1",
      "updated": "2003-12-27T22:20:52.000Z"
    }
  ],
  "analyses": {
    "keywords": [
      "composition",
      "galactic bulge stars",
      "solar neighborhood trends",
      "si enhancements",
      "supernova events"
    ],
    "note": {
      "typesetting": "TeX",
      "pages": 0,
      "language": "en",
      "license": "arXiv",
      "status": "editable",
      "inspire": 636405
    }
  }
}