{
  "id": "1905.06935",
  "version": "v1",
  "published": "2019-05-16T17:55:02.000Z",
  "updated": "2019-05-16T17:55:02.000Z",
  "title": "Electron Densities and Nitrogen Abundances in Ionized Gas Derived Using [NII] Fine-structure and Hydrogen Recombination lines",
  "authors": [
    "Jorge L. Pineda",
    "Shinji Horiuchi",
    "L. D. Anderson",
    "Matteo Luisi",
    "Paul F. Goldsmith",
    "William D. Langer",
    "Thomas B. H. Kuiper",
    "Geoff Bryden",
    "Melissa Soriano",
    "Joseph W. Lazio"
  ],
  "comment": "18 pages, 9 figures, to be submitted to ApJ, comments welcome",
  "categories": [
    "astro-ph.GA"
  ],
  "abstract": "We present a method for deriving the electron density of ionized gas using the ratio of the intensity of the [NII] 205um line to that of a Hydrogen radio recombination line (RRL). We use this method to derive electron densities of 21 velocity components in 11 lines of sight, including the Galactic center. We observed, at high--spectral resolution, the [NII] 205um with the Herschel/HIFI and SOFIA/GREAT instruments and the radio recombination lines with the Green Bank Telescope and the NASA Deep Space Network Deep Space Station 43 (DSS-43) telescope. We find typical electron densities between 6 to 170 cm^{-3}, which are consistent with those derived at low spectral resolution using the [NII] 205um/122um ratio with Herschel/PACS on a larger sample of sight lines in the Galactic plane. By matching the electron densities derived from the [NII] 205um/RRL intensity ratio and the [NII] 122um/205um intensity ratio, we derive the nitrogen fractional abundance for our velocity components. We investigate the dependence of the N/H ratio with Galactocentric distance in the inner Galaxy (R_gal<6kpc), which is inaccessible in optical studies due to dust extinction. We find that the distribution of nitrogen abundances in the inner galaxy derived from our data has a slope that is consistent to that found in the outer Galaxy in optical studies. This result is inconsistent with some suggestions of a flatter distribution of the nitrogen abundance in the inner galaxy.",
  "revisions": [
    {
      "version": "v1",
      "updated": "2019-05-16T17:55:02.000Z"
    }
  ],
  "analyses": {
    "keywords": [
      "electron density",
      "nitrogen abundance",
      "hydrogen recombination lines",
      "ionized gas",
      "space network deep space"
    ],
    "note": {
      "typesetting": "TeX",
      "pages": 18,
      "language": "en",
      "license": "arXiv",
      "status": "editable"
    }
  }
}