{
  "id": "1608.00996",
  "version": "v1",
  "published": "2016-08-02T20:41:24.000Z",
  "updated": "2016-08-02T20:41:24.000Z",
  "title": "ALMA Observations of Orion Source I at 350 and 660 GHz",
  "authors": [
    "R. L. Plambeck",
    "M. C. H. Wright"
  ],
  "comment": "17 pages, 14 figures; submitted to ApJ",
  "categories": [
    "astro-ph.GA",
    "astro-ph.SR"
  ],
  "abstract": "Orion Source I ('SrcI') is the protostar at the center of the Kleinmann-Low Nebula. ALMA observations of SrcI at 350 and 660 GHz failed to detect the H26$\\alpha$ and H21$\\alpha$ recombination lines, ruling out the possibility that SrcI is a hypercompact HII region. The deconvolved size of the continuum source is approximately 0.23 x 0.05\" (100 x 20 AU); it is interpreted as a disk viewed almost edge-on. The continuum flux density is proportional to $\\nu^2$ from 43 GHz to 350 GHz, then increases slightly faster than $\\nu^2$ from 350 GHz to 660 GHz. Optically thick thermal emission from ~500 K dust is the most plausible source of the continuum, even at frequencies as low as 43 GHz; the disk mass is most likely in the range 0.02-0.2 Mo. A rich spectrum of molecular lines is detected, mostly from sulfur- and silicon-rich molecules like SO, SO$_2$, and SiS, but also including vibrationally excited CO and several unidentified transitions. Lines with upper energy levels E$_U$ > 500 K appear in emission and are symmetric about the source's LSR velocity of 5 km/sec, while lines with E$_U$ < 500 K appear as blueshifted absorption features against the continuum, indicating that they originate in outflowing gas. The emission lines exhibit a velocity gradient along the major axis of the disk that is consistent with rotation around a 5-7 Mo central object. The relatively low mass of SrcI and the existence of a 100 AU disk around it are incompatible with the model in which SrcI and the nearby Becklin-Neugebauer Object were ejected from a multiple system 500 years ago.",
  "revisions": [
    {
      "version": "v1",
      "updated": "2016-08-02T20:41:24.000Z"
    }
  ],
  "analyses": {
    "keywords": [
      "alma observations",
      "orion source",
      "sources lsr velocity",
      "mo central object",
      "continuum flux density"
    ],
    "note": {
      "typesetting": "TeX",
      "pages": 17,
      "language": "en",
      "license": "arXiv",
      "status": "editable"
    }
  }
}