{
  "id": "2405.00097",
  "version": "v1",
  "published": "2024-04-30T18:00:01.000Z",
  "updated": "2024-04-30T18:00:01.000Z",
  "title": "Evidence for a toroidal magnetic field in the core of 3C 84",
  "authors": [
    "G. F. Paraschos",
    "L. C. Debbrecht",
    "J. A. Kramer",
    "E. Traianou",
    "I. Liodakis",
    "T. P. Krichbaum",
    "J. -Y. Kim",
    "M. Janssen",
    "D. G. Nair",
    "T. Savolainen",
    "E. Ros",
    "U. Bach",
    "J. A. Hodgson",
    "M. Lisakov",
    "N. R. MacDonald",
    "J. A. Zensus"
  ],
  "comment": "10 pages, 8 figures, accepted for publication in Astronomy and Astrophysics",
  "categories": [
    "astro-ph.HE",
    "astro-ph.GA"
  ],
  "abstract": "The spatial scales of relativistic radio jets, probed by relativistic magneto-hydrodynamic jet launching simulations (RMHDs) and by most very-long-baseline interferometry (VLBI) observations differ by an order of magnitude. Bridging the gap between these RMHD simulations and VLBI observations requires selecting nearby active galactic nuclei (AGN), the parsec-scale region of which can be resolved. 3C 84 is a nearby bright AGN fulfilling the necessary requirements: it is launching a powerful, relativistic jet powered by a central supermassive black hole, while also being very bright. Using 22 GHz global VLBI measurements of 3C 84 we aim to study its sub-parsec region in both total intensity and linear polarisation, to explore the properties of this jet, with a linear resolution of $\\sim0.1$ parsec. We test different simulation setups by altering the bulk Lorentz factor $\\Gamma$ of the jet, as well as the magnetic field configuration (toroidal, poloidal, helical). We confirm the persistence of a limb brightened structure, which reaches deep into the sub-parsec region. The corresponding electric vector position angles (EVPAs) follow the bulk jet flow inside but tend to be orthogonal to it near the edges. Our state-of-the-art RMHD simulations show that this geometry is consistent with a spine-sheath model, associated with a mildly relativistic flow and a toroidal magnetic field configuration.",
  "revisions": [
    {
      "version": "v1",
      "updated": "2024-04-30T18:00:01.000Z"
    }
  ],
  "analyses": {
    "keywords": [
      "toroidal magnetic field",
      "electric vector position angles",
      "nearby active galactic nuclei",
      "magnetic field configuration",
      "ghz global vlbi measurements"
    ],
    "note": {
      "typesetting": "TeX",
      "pages": 10,
      "language": "en",
      "license": "arXiv",
      "status": "editable"
    }
  }
}