{
  "id": "2007.10474",
  "version": "v1",
  "published": "2020-07-20T21:02:17.000Z",
  "updated": "2020-07-20T21:02:17.000Z",
  "title": "Gamma-ray emission in radio galaxies under the VLBI scope -- II. The relationship between gamma-ray emission and parsec-scale jets in radio galaxies",
  "authors": [
    "R. Angioni",
    "E. Ros",
    "M. Kadler",
    "R. Ojha",
    "C. Müller",
    "P. G. Edwards",
    "P. R. Burd",
    "B. Carpenter",
    "M. S. Dutka",
    "S. Gulyaev",
    "H. Hase",
    "S. Horiuchi",
    "F. Krauß",
    "J. E. J. Lovell",
    "T. Natusch",
    "C. Phillips",
    "C. Plötz",
    "J. F. H. Quick",
    "F. Rösch",
    "R. Schulz",
    "J. Stevens",
    "A. K. Tzioumis",
    "S. Weston",
    "J. Wilms",
    "J. A. Zensus"
  ],
  "comment": "Main text: 15 pages, 12 figures, 6 tables. Appendix: 14 pages, 20 figures, 13 tables. Accepted for publication in Astronomy and Astrophysics",
  "categories": [
    "astro-ph.HE"
  ],
  "abstract": "Following our study of the radio and high-energy properties of $\\gamma$-ray-emitting radio galaxies, here we investigate the kinematic and spectral properties of the parsec-scale jets of radio galaxies that have not yet been detected by Fermi-LAT. We take advantage of the regular VLBI observations provided by the TANAMI monitoring program, and explore the kinematic properties of six $\\gamma$-ray-faint radio galaxies. We include publicly available VLBI kinematics of $\\gamma$-ray-quiet radio galaxies monitored by the MOJAVE program and perform a Fermi-LAT analysis, deriving upper limits. We combine these results with those from our previous paper to construct the largest sample of radio galaxies with combined VLBI and $\\gamma$-ray measurements to date. We find superluminal motion up to $\\beta_\\mathrm{app}=3.6$ in the jet of PKS 2153$-$69. We find a clear trend of higher apparent speed as a function of distance from the jet core on scales of $\\sim10^5\\,R_s$, corresponding to the end of the collimation and acceleration zone in nearby radio galaxies. We find evidence of subluminal apparent motion in the jets of PKS 1258$-$321 and IC 4296, and no measurable motion for PKS 1549$-$79, PKS 1733$-$565 and PKS 2027$-$308. We compare the VLBI properties of $\\gamma$-ray-detected and undetected radio galaxies, and find significantly different distributions of median core flux density, and, possibly, of median core brightness temperature. We find a significant correlation between median core flux density and $\\gamma$-ray flux, but no correlation with typical Doppler boosting indicators such as median core brightness temperature and core dominance. Our study suggests that high-energy emission from radio galaxies is related to parsec-scale radio emission from the inner jet, but is not driven by Doppler boosting effects, in contrast to the situation in their blazar counterparts.",
  "revisions": [
    {
      "version": "v1",
      "updated": "2020-07-20T21:02:17.000Z"
    }
  ],
  "analyses": {
    "keywords": [
      "radio galaxies",
      "gamma-ray emission",
      "parsec-scale jets",
      "median core flux density",
      "vlbi scope"
    ],
    "note": {
      "typesetting": "TeX",
      "pages": 15,
      "language": "en",
      "license": "arXiv",
      "status": "editable"
    }
  }
}