{
  "id": "1907.12776",
  "version": "v1",
  "published": "2019-07-30T08:29:37.000Z",
  "updated": "2019-07-30T08:29:37.000Z",
  "title": "Nobeyama 45-m Cygnus~X CO Survey: (2) Physical Properties of $\\mathrm{C^{18}O}$ Clumps",
  "authors": [
    "Tatsuya Takekoshi",
    "Shinji Fujita",
    "Atsushi Nishimura",
    "Kotomi Taniguchi",
    "Mitsuyoshi Yamagishi",
    "Mitsuhiro Matsuo",
    "Satoshi Ohashi",
    "Kazuki Tokuda",
    "Tetsuhiro Minamidani"
  ],
  "comment": "20 pages, 7 figures, accepted for publication in the Astrophysical Journal",
  "categories": [
    "astro-ph.GA"
  ],
  "abstract": "We report the statistical physical properties of the C$^{18}$O($J=1-0$) clumps present in a prominent cluster-forming region, Cygnus X, using the dataset obtained by the Nobeyama 45-m radio telescope. This survey covers 9 deg$^2$ of the north and south regions of Cygnus X, and totally 174 C$^{18}$O clumps are identified using the dendrogram method. Assuming a distance of 1.4 kpc, these clumps have radii of 0.2-1 pc, velocity dispersions of $<2.2~\\mathrm{km~s^{-1}}$, gas masses of 30-3000 $M_\\odot$, and H$_2$ densities of (0.2-5.5)$\\times10^4~\\mathrm{cm^{-3}}$. We confirm that the C$^{18}$O clumps in the north region have a higher H$_2$ density than those in the south region, supporting the existence of a difference in the evolution stages, consistent with the star formation activity of these regions. The difference in the clump properties of the star-forming and starless clumps is also confirmed by the radius, velocity dispersion, gas mass, and H$_2$ density. The average virial ratio of 0.3 supports that these clumps are gravitationally bound. The C$^{18}$O clump mass function shows two spectral index components, $\\alpha=-1.4$ in 55-140 $M_\\odot$ and $\\alpha=-2.1$ in $>140~M_\\odot$, which are consistent with the low- and intermediate-mass parts of the Kroupa's initial mass function. The spectral index in the star-forming clumps in $>140~M_\\odot$ is consistent with that of the starless clumps in 55-140 $M_\\odot$, suggesting that the latter will evolve into star-forming clumps while retaining the gas accretion. Assuming a typical star formation efficiency of molecular clumps (10%), about ten C$^{18}$O clumps having a gas mass of $>10^3~M_\\odot$ will evolve into open clusters containing one or more OB stars.",
  "revisions": [
    {
      "version": "v1",
      "updated": "2019-07-30T08:29:37.000Z"
    }
  ],
  "analyses": {
    "keywords": [
      "physical properties",
      "gas mass",
      "kroupas initial mass function",
      "velocity dispersion",
      "south region"
    ],
    "note": {
      "typesetting": "TeX",
      "pages": 20,
      "language": "en",
      "license": "arXiv",
      "status": "editable"
    }
  }
}