{
  "id": "1706.05659",
  "version": "v1",
  "published": "2017-06-18T14:21:29.000Z",
  "updated": "2017-06-18T14:21:29.000Z",
  "title": "Molecular gas in a compact H{\\sc ii} region RCW 166; possible evidence for an early phase of cloud-cloud collision prior to the bubble formation (Draft 6/18)",
  "authors": [
    "Akio Ohama",
    "Mikito Kono",
    "Daichi Tsutsumi",
    "Yusuke Hattori",
    "Kazufumi Torii",
    "Atsushi Nishimura",
    "Hidetoshi Sano",
    "Hiroaki Yamamoto",
    "Kengo Tachihara",
    "Yasuo Fukui"
  ],
  "comment": "21 pages, 9 figures",
  "categories": [
    "astro-ph.GA"
  ],
  "abstract": "Young HII regions are an important site to study O star formation based on distributions of ionized and molecular gas. We revealed that two molecular clouds at 48 km s-1 and 53 km s-1 are associated with a compact HII region RCW 166 by using the JCMT High-Resolution Survey (COHRS) of the 12CO (J=3-2) emission (Dempsey et al. 2013). RCW 166 comprises a bright ring at 8 um and an elongated compact HII region inside the ring. The 48 km s-1 cloud delineates the ring, and the 53 km s-1 cloud is located within the ring, indicating a complementary distribution between the two molecular components. We propose a hypothesis that RCW 166 was formed by triggering in cloud-cloud collision at a projected velocity separation of 5 km s-1. The compact HII region is located toward the inner cloud which was impacted in the collision. We argue that RCW 166 is in an earliy evolutionary stage, ~ 0.1 Myr after the collision according to the scheme by Habe & Ohta (1992) which will be followed by a bubble formation stage like RCW 120. Inoue & Fukui (2013) showed that the interface gas becomes highly turbulent and realizes a high-mass accretion rate of 10-3 - 10-4 Mo/yr by magneto- hydrodynamical numerical simulations, which offers an explanation of the O star formation in RCW 166.",
  "revisions": [
    {
      "version": "v1",
      "updated": "2017-06-18T14:21:29.000Z"
    }
  ],
  "analyses": {
    "keywords": [
      "cloud-cloud collision prior",
      "region rcw",
      "molecular gas",
      "bubble formation",
      "early phase"
    ],
    "note": {
      "typesetting": "TeX",
      "pages": 21,
      "language": "en",
      "license": "arXiv",
      "status": "editable"
    }
  }
}