{
  "id": "1605.09381",
  "version": "v1",
  "published": "2016-05-30T20:00:01.000Z",
  "updated": "2016-05-30T20:00:01.000Z",
  "title": "ALMA Resolves the Nuclear Disks of Arp 220",
  "authors": [
    "Nick Scoville",
    "Lena Murchikova",
    "Fabian Walter",
    "Catherine Vlahakis",
    "Jin Koda",
    "Paul Vanden Bout",
    "Joshua Barnes",
    "Lars Hernquist",
    "Kartik Sheth",
    "Min Yun",
    "David Sanders",
    "Lee Armus",
    "Pierre Cox",
    "Todd Thompson",
    "Brant Robertson",
    "Laura Zschaechner",
    "Linda Tacconi",
    "Paul Torrey",
    "Christopher C. Hayward",
    "Reinhard Genzel",
    "Phil Hopkins",
    "Paul van der Werf",
    "Roberto Decarli"
  ],
  "comment": "submitted to ApJ",
  "categories": [
    "astro-ph.GA"
  ],
  "abstract": "We present 90 mas (37 pc) resolution ALMA imaging of Arp 220 in the CO (1-0) line and continuum at $\\lambda = 2.6$ mm. The internal gas distribution and kinematics of both galactic nuclei are well-resolved for the first time.In the more luminous West nucleus, the major gas and dust emission extends to 0.2\\arcsec radius (80 pc); the central resolution element shows a strong peak in the dust emission but a factor 3 dip in the CO line emission. In this nucleus, the dust is apparently optically thick ($\\tau_{\\rm 2.6mm} \\sim1$) at $\\lambda = 2.6$ mm with a dust emission brightness temperature $\\sim120$ K. The column of ISM at this nucleus is $\\rm N_{H2} \\geq 2\\times10^{26}$ cm$^{-2}$, corresponding to A$_V = 10^6$ mag and 1000 gr cm$^{-2}$. The East nucleus is somewhat more elongated with radial extent 0.3\\arcsec or $\\sim120$ pc. The derived kinematics of the nuclear disks provide a good fit to the line profiles sampled every 50 mas, yielding the emissivity distributions, the rotation curves and velocity dispersions. In the West nucleus, there is evidence of a central Keplerian component requiring a central mass of $8\\times10^8$ \\msun. The intrinsic widths of the emission lines are $\\Delta \\rm v (FWHM)$ = 250 (West) and 120 (East) \\kms.Given the very short dissipation timescales for turbulence ($\\lesssim10^5$ yrs) if these motions are dispersive, we suggest that the local line widths may be the result of semi-coherent motions (e.g. a tightly wound spiral pattern) within the nuclear disks.The overall symmetry of the nuclear disk structures is most impressive -- implying the merger timescale is significantly longer than the rotation period of the disks ($\\sim1$ Myr) so that the disks can relax.",
  "revisions": [
    {
      "version": "v1",
      "updated": "2016-05-30T20:00:01.000Z"
    }
  ],
  "analyses": {
    "keywords": [
      "nuclear disk",
      "alma resolves",
      "west nucleus",
      "dust emission brightness temperature",
      "internal gas distribution"
    ],
    "note": {
      "typesetting": "TeX",
      "pages": 0,
      "language": "en",
      "license": "arXiv",
      "status": "editable"
    }
  }
}