{
  "id": "1610.03853",
  "version": "v1",
  "published": "2016-10-12T20:00:02.000Z",
  "updated": "2016-10-12T20:00:02.000Z",
  "title": "IMF and [Na/Fe] abundance ratios from optical and NIR Spectral Features in Early-type Galaxies",
  "authors": [
    "F. La Barbera",
    "A. Vazdekis",
    "I. Ferreras",
    "A. Pasquali",
    "C. Allende Prieto",
    "B. Rock",
    "D. S. Aguado",
    "R. F. Peletier"
  ],
  "comment": "22 pages, 8 figure, accepted for publication in MNRAS. The new Na-enhanced models will be available soon at http://miles.iac.es/",
  "categories": [
    "astro-ph.GA"
  ],
  "abstract": "We present a joint analysis of the four most prominent sodium-sensitive features (NaD, NaI8190, NaI1.14, and NaI2.21), in the optical and Near-Infrared spectral range, of two nearby, massive (sigma~300km/s), early-type galaxies (named XSG1 and XSG2). Our analysis relies on deep VLT/X-Shooter long-slit spectra, along with newly developed stellar population models, allowing for [Na/Fe] variations, up to 1.2dex, over a wide range of age, total metallicity, and IMF slope. The new models show that the response of the Na-dependent spectral indices to [Na/Fe] is stronger when the IMF is bottom heavier. For the first time, we are able to match all four Na features in the central regions of massive early-type galaxies, finding an overabundance of [Na/Fe], in the range 0.5-0.7dex, and a bottom-heavy IMF. Therefore, individual abundance variations cannot be fully responsible for the trends of gravity-sensitive indices, strengthening the case towards a non-universal IMF. Given current limitations of theoretical atmosphere models, our [Na/Fe] estimates should be taken as upper limits. For XSG1, where line strengths are measured out to 0.8Re, the radial trend of [Na/Fe] is similar to [Mg/Fe] and [C/Fe], being constant out to 0.5Re, and decreasing by 0.2-0.3dex at 0.8Re, without any clear correlation with local metallicity. Such a result seems to be in contrast with the predicted increase of Na nucleosynthetic yields from AGB stars and TypeII SNe. For XSG1, the Na-inferred IMF radial profile is consistent, within the errors, with that derived from TiO features and the Wing-Ford band, presented in a recent paper.",
  "revisions": [
    {
      "version": "v1",
      "updated": "2016-10-12T20:00:02.000Z"
    }
  ],
  "analyses": {
    "keywords": [
      "early-type galaxies",
      "nir spectral features",
      "abundance ratios",
      "developed stellar population models",
      "deep vlt/x-shooter long-slit spectra"
    ],
    "note": {
      "typesetting": "TeX",
      "pages": 22,
      "language": "en",
      "license": "arXiv",
      "status": "editable"
    }
  }
}