{
  "id": "1704.00739",
  "version": "v1",
  "published": "2017-04-03T18:00:45.000Z",
  "updated": "2017-04-03T18:00:45.000Z",
  "title": "Characterizing the transition from diffuse atomic to dense molecular clouds in the Magellanic clouds with [CII], [CI], and CO",
  "authors": [
    "Jorge L. Pineda",
    "William D. Langer",
    "Paul F. Goldsmith",
    "Shinji Horiuchi",
    "Thomas B. H. Kuiper",
    "Erik Muller",
    "Annie Hughes",
    "Juergen Ott",
    "Thangasamy Velusamy",
    "Tony Wong"
  ],
  "comment": "32 pages, 21 figures, Accepted to ApJ",
  "categories": [
    "astro-ph.GA"
  ],
  "abstract": "We present and analyze deep Herschel/HIFI observations of the [CII] 158um, [CI] 609um, and [CI] 370um lines towards 54 lines-of-sight (LOS) in the Large and Small Magellanic clouds. These observations are used to determine the physical conditions of the line--emitting gas, which we use to study the transition from atomic to molecular gas and from C^+ to C^0 to CO in their low metallicity environments. We trace gas with molecular fractions in the range 0.1<f(H2)<1, between those in the diffuse H2 gas detected by UV absorption (f(H2)<0.2) and well shielded regions in which hydrogen is essentially completely molecular. The C^0 and CO column densities are only measurable in regions with molecular fractions f(H2)>0.45 in both the LMC and SMC. Ionized carbon is the dominant gas-phase form of this element that is associated with molecular gas, with C^0 and CO representing a small fraction, implying that most (89% in the LMC and 77% in the SMC) of the molecular gas in our sample is CO-dark H2. The mean X_CO conversion factors in our LMC and SMC sample are larger than the value typically found in the Milky Way. When applying a correction based on the filling factor of the CO emission, we find that the values of X_CO in the LMC and SMC are closer to that in the Milky Way. The observed [CII] intensity in our sample represents about 1% of the total far-infrared intensity from the LOSs observed in both Magellanic Clouds.",
  "revisions": [
    {
      "version": "v1",
      "updated": "2017-04-03T18:00:45.000Z"
    }
  ],
  "analyses": {
    "keywords": [
      "dense molecular clouds",
      "diffuse atomic",
      "molecular gas",
      "transition",
      "analyze deep herschel/hifi observations"
    ],
    "note": {
      "typesetting": "TeX",
      "pages": 32,
      "language": "en",
      "license": "arXiv",
      "status": "editable"
    }
  }
}