{
  "id": "2007.15708",
  "version": "v1",
  "published": "2020-07-30T19:49:41.000Z",
  "updated": "2020-07-30T19:49:41.000Z",
  "title": "The PDR structure and kinematics around the compact HII regions S235A and S235C with [CII], [13CII], [OI] and HCO+ line profiles",
  "authors": [
    "M. S. Kirsanova",
    "V. Ossenkopf-Okada",
    "L. D. Anderson",
    "P. A. Boley",
    "J. H. Bieging",
    "Ya. N. Pavlyuchenkov",
    "M. Luisi",
    "N. Schneider",
    "M. Andersen",
    "M. R. Samal",
    "A. M. Sobolev",
    "C. Buchbender",
    "R. Aladro",
    "Y. Okada"
  ],
  "comment": "accepted to MNRAS",
  "doi": "10.1093/mnras/staa2142",
  "categories": [
    "astro-ph.GA",
    "astro-ph.SR"
  ],
  "abstract": "The aim of the present work is to study structure and gas kinematics in the photodissociation regions (PDRs) around the compact HII regions S235A and S235C. We observe the [CII], [13CII] and [OI] line emission, using SOFIA/upGREAT and complement them by data of HCO+ and CO. We use the [13CII] line to measure the optical depth of the [CII] emission, and find that the [CII] line profiles are influenced by self-absorption, while the [13CII] line remains unaffected by these effects. Hence, for dense PDRs, [13CII] emission is a better tracer of gas kinematics. The optical depth of the [CII] line is up to 10 in S235A. We find an expanding motion of the [CII]-emitting layer of the PDRs into the front molecular layer in both regions. Comparison of the gas and dust columns shows that gas components visible neither in the [CII] nor in low-J CO lines may contribute to the total column across S235A. We test whether the observed properties of the PDRs match the predictions of spherical models of expanding HII region + PDR + molecular cloud. Integrated intensities of the [13CII], [CII] and [OI] lines are well-represented by the model, but the models do not reproduce the double-peaked [CII] line profiles due to an insufficient column density of C+. The model predicts that the [OI] line could be a more reliable tracer of gas kinematics, but the foreground self-absorbing material does not allow using it in the considered regions.",
  "revisions": [
    {
      "version": "v1",
      "updated": "2020-07-30T19:49:41.000Z"
    }
  ],
  "analyses": {
    "keywords": [
      "compact hii regions s235a",
      "line profiles",
      "pdr structure",
      "gas kinematics",
      "front molecular layer"
    ],
    "tags": [
      "journal article"
    ],
    "note": {
      "typesetting": "TeX",
      "pages": 0,
      "language": "en",
      "license": "arXiv",
      "status": "editable"
    }
  }
}