{
  "id": "astro-ph/0207082",
  "version": "v1",
  "published": "2002-07-03T09:53:05.000Z",
  "updated": "2002-07-03T09:53:05.000Z",
  "title": "Proper motion in Cygnus A",
  "authors": [
    "U. Bach",
    "T. P. Krichbaum",
    "W. Alef",
    "A. Witzel",
    "J. A. Zensus"
  ],
  "comment": "4 pages, 6 figures, appears in: Proceedings of the 6th European VLBI Network Symposium held on June 25th-28th in Bonn, Germany. Edited by: E. Ros, R.W. Porcas, A.P. Lobanov, and J.A. Zensus",
  "categories": [
    "astro-ph"
  ],
  "abstract": "Our recent VLBI observations of the prominent FR II radio galaxy Cygnus A with the EVN and the VLBA reveal a pronounced two-sided jet structure. At 5 GHz, we now have 4 epochs from 1986, 1991 (Carilli et al., 1991 & 1994), 1996 and 2002 from which we could derive the kinematics of the jet and counter-jet. On the jet side and on mas scales, the jet seems to accelerate from $\\beta_{\\rm app}\\approx 0.1-0.2$ (Krichbaum et al. 1998) at core-separations near 1 mas to $\\beta_{\\rm app}\\approx 0.4-0.6$ at $r \\geq 4$ mas ($H_0=100$ km s$^{-1}$ Mpc$^{-1}$, $q_0=0.5$). For the first time we also measure significant structural variability on the counter-jet side. For this, we derive a motion of $\\beta_{\\rm app}=0.35\\pm0.2$ at $r=9.5$ mas. The flat spectrum of the inner region of the counter-jet (free-free absorption) and the frequency dependence of the jet to counter-jet ratio support strong evidence for an obscuring torus in front of the counter-jet (Bach et al. in prep, Krichbaum et al. 1998).",
  "revisions": [
    {
      "version": "v1",
      "updated": "2002-07-03T09:53:05.000Z"
    }
  ],
  "analyses": {
    "keywords": [
      "proper motion",
      "counter-jet ratio support strong evidence",
      "measure significant structural variability",
      "radio galaxy cygnus",
      "frequency dependence"
    ],
    "note": {
      "typesetting": "TeX",
      "pages": 4,
      "language": "en",
      "license": "arXiv",
      "status": "editable",
      "inspire": 589738
    }
  }
}