{
  "id": "0704.0272",
  "version": "v1",
  "published": "2007-04-02T21:32:32.000Z",
  "updated": "2007-04-02T21:32:32.000Z",
  "title": "A Comparison between Anomalous 6-cm H$_2$CO Absorption and CO(1-0) Emission in the L1204/S140",
  "authors": [
    "Monica Ivette Rodriguez",
    "Tommy Wiklind",
    "Ronald J. Allen",
    "Vladimir Escalante",
    "Laurent Loinard"
  ],
  "comment": "9 pages 6 figures ApJ:accepted",
  "journal": "Astrophys.J.663:824-833,2007",
  "doi": "10.1086/518553",
  "categories": [
    "astro-ph"
  ],
  "abstract": "We report observations of the dust cloud L1204 with the Onsala 25-m telescope in the 6 cm (1$_{11}-1_{10}$) transition of \\htco. The observed region includes the S140 H${\\alpha}$ arc. This spectral line is seen here in absorption against the cosmic microwave background, indicating the presence of widespread warm molecular gas at intermediate densities. Overall, the distributions of H$_2$CO and CO (taken from the literature) are fairly similar, though significant differences exist at small scales. Most notably, while the CO peak is nearly coincident with the S140 H${\\alpha}$ arc, the maximum H$_2$CO absorption is clearly separated from it by a full 10$'$ beam ($\\sim$ 3 pc). We argue that these differences result from differing abundances and excitation requirements. The CO(1-0) line is more optically thick and more biased towards warm gas than the H$_2$CO 6 cm line. On the other hand, formaldehyde is more easily photodissociated and is, therefore, a poorer tracer of the molecular gas located immediately behind Photon Dominated Regions.",
  "revisions": [
    {
      "version": "v1",
      "updated": "2007-04-02T21:32:32.000Z"
    }
  ],
  "analyses": {
    "keywords": [
      "absorption",
      "comparison",
      "l1204/s140",
      "widespread warm molecular gas",
      "dust cloud l1204"
    ],
    "tags": [
      "journal article"
    ],
    "publication": {
      "journal": "The Astrophysical Journal",
      "year": 2007,
      "month": "Jul",
      "volume": 663,
      "number": 2,
      "pages": 824
    },
    "note": {
      "typesetting": "TeX",
      "pages": 9,
      "language": "en",
      "license": "arXiv",
      "status": "editable",
      "inspire": 747756,
      "adsabs": "2007ApJ...663..824R"
    }
  }
}