{
  "id": "2001.04386",
  "version": "v1",
  "published": "2020-01-13T16:41:27.000Z",
  "updated": "2020-01-13T16:41:27.000Z",
  "title": "The Proper Motion of Sagittarius A*: III. The Case for a Supermassive Black Hole",
  "authors": [
    "M. J. Reid",
    "A. Brunthaler"
  ],
  "comment": "19 pages, 4 figures and 4 tables",
  "categories": [
    "astro-ph.GA"
  ],
  "abstract": "We report measurements with the Very Long Baseline Array of the proper motion of Sgr A* relative to two extragalactic radio sources spanning 18 years. The apparent motion of Sgr A* is -6.411 +/- 0.008 mas/yr along the Galactic plane and -0.219 +/- 0.007 mas/yr toward the North Galactic Pole. This apparent motion can almost entirely be attributed to the effects of the Sun's orbit about the Galactic center. Removing these effects yields residuals of -0.58 +/- 2.23 km/s in the direction of Galactic rotation and -0.85 +/- 0.75 km/s toward the North Galactic Pole. A maximum-likelihood analysis of the motion, both in the Galactic plane and perpendicular to it, expected for a massive object within the Galactic center stellar cluster indicates that the radiative source, Sgr A*, contains more than about 25% of the gravitational mass of 4 x 10^6 Msun deduced from stellar orbits. The intrinsic size of Sgr A* is comparable to its Schwarzschild radius, and the implied mass density of >4 x 10^23 Msun/pc^-3 very close to that expected for a black hole, providing overwhelming evidence that it is indeed a super-massive black hole. Finally, the existence of \"intermediate-mass\" black holes more massive than 3 x 10^4 Msun between approximately 0.003 and 0.1 pc from Sgr A*are excluded.",
  "revisions": [
    {
      "version": "v1",
      "updated": "2020-01-13T16:41:27.000Z"
    }
  ],
  "analyses": {
    "keywords": [
      "supermassive black hole",
      "proper motion",
      "north galactic pole",
      "apparent motion",
      "sagittarius"
    ],
    "note": {
      "typesetting": "TeX",
      "pages": 19,
      "language": "en",
      "license": "arXiv",
      "status": "editable"
    }
  }
}