{
  "id": "1212.1540",
  "version": "v1",
  "published": "2012-12-07T06:46:40.000Z",
  "updated": "2012-12-07T06:46:40.000Z",
  "title": "ARGOS III: Stellar Populations in the Galactic Bulge of the Milky Way",
  "authors": [
    "M. Ness",
    "K. Freeman",
    "E. Athanassoula",
    "E. Wylie de Boer",
    "J. Bland Hawthorn",
    "M. Asplund",
    "G. F. Lewis",
    "D. Yong",
    "R. R. Lane",
    "L. L. Kiss"
  ],
  "comment": "Accepted MNRAS, 21 pages, 20 figures, 6 tables",
  "categories": [
    "astro-ph.GA"
  ],
  "abstract": "We present the metallicity results from the ARGOS spectroscopic survey of the Galactic bulge. Our aim is to understand the formation of the Galactic bulge: did it form via mergers, as expected from Lambda CDM theory, or from disk instabilities, as suggested by its boxy/peanut shape, or both? We have obtained spectra for 28,000 stars at a spectral resolution of R = 11,000. From these spectra, we have determined stellar parameters and distances to an accuracy of < 1.5 kpc. The stars in the inner Galaxy span a large range in [Fe/H], -2.8 < [Fe/H] < +0.6. From the spatial distribution of the red clump stars as a function of [Fe/H] (Ness et al. 2012a), we propose that the stars with [Fe/H] > -0.5 are part of the boxy/peanut bar/bulge. We associate the lower metallicity stars ([Fe/H] < -0.5) with the thick disk, which may be puffed up in the inner region, and with the inner regions of the metal-weak thick disk and inner halo. For the bulge stars with [Fe/H] > -0.5, we find two discrete populations; (i) stars with [Fe/H] ~ -0.25 which provide a roughly constant fraction of the stars in the latitude interval b = -5 deg to -10 deg, and (ii) a kinematically colder, more metal-rich population with mean [Fe/H] ~ +0.15 which is more prominent closer to the plane. The changing ratio of these components with latitude appears as a vertical abundance gradient of the bulge. We attribute both of these bulge components to instability-driven bar/bulge formation from the thin disk. We do not exclude a weak underlying classical merger-generated bulge component, but see no obvious kinematic association of any of our bulge stars with such a classical bulge component. [abridged]",
  "revisions": [
    {
      "version": "v1",
      "updated": "2012-12-07T06:46:40.000Z"
    }
  ],
  "analyses": {
    "keywords": [
      "galactic bulge",
      "milky way",
      "stellar populations",
      "classical merger-generated bulge component",
      "underlying classical merger-generated bulge"
    ],
    "tags": [
      "journal article"
    ],
    "publication": {
      "doi": "10.1093/mnras/sts629",
      "journal": "Monthly Notices of the Royal Astronomical Society",
      "year": 2013,
      "month": "Apr",
      "volume": 430,
      "number": 2,
      "pages": 836
    },
    "note": {
      "typesetting": "TeX",
      "pages": 21,
      "language": "en",
      "license": "arXiv",
      "status": "editable",
      "inspire": 1206287,
      "adsabs": "2013MNRAS.430..836N"
    }
  }
}