{
  "id": "1611.06573",
  "version": "v1",
  "published": "2016-11-20T19:13:59.000Z",
  "updated": "2016-11-20T19:13:59.000Z",
  "title": "Dynamical friction and the evolution of Supermassive Black hole Binaries: the final hundred-parsec problem",
  "authors": [
    "Fani Dosopoulou",
    "Fabio Antonini"
  ],
  "comment": "17 pages, 11 Figures. Submitted to AAS Journals",
  "categories": [
    "astro-ph.GA",
    "gr-qc"
  ],
  "abstract": "The massive black holes originally in the nuclei of two merging galaxies will form a binary in the core of the merger remnant. The early evolution of the massive binary is driven by dynamical friction before the binary becomes \"hard\" and eventually reaches coalescence through the emission of gravitational wave radiation. We use analytical models and $N$-body integrations to study the evolution of supermassive black hole binaries due to dynamical friction. In our treatment we include the frictional force from stars moving faster than the massive body which is neglected in the standard Chandrasekhar's treatment. We show that the eccentricity of a massive binary increases due to dynamical friction if the density profile of the surrounding stellar cusp rises less steeply than $\\rho\\propto r^{-2}$. For cusps shallower than $\\rho\\propto r^{-1}$ the dynamical fiction timescale can become very long due to the deficit of stars moving slower than the secondary hole. Although adding the contribution of the fast stars increases the orbital decay rate, sufficiently low mass ratio binaries ($q\\lesssim 10^{-3}$) in sufficiently massive host galaxies have decay timescales that are longer than one Hubble time. During such minor mergers the secondary hole stalls on an eccentric orbit at a galactocentric distance of order one tenth the influence radius of the primary black hole (i.e., $\\approx 10-100$ pc for massive ellipticals). We calculate the expected average number of stalled satellites as a function of the host galaxy black hole mass, and find that the brightest cluster galaxies should have $\\gtrsim 1$ of such satellites orbiting within their inner cores. Our results could provide an explanation for a number of observational puzzles, which include double structures or the presence of multiple nuclei in core elliptical galaxies, off-center active galactic nuclei and eccentric nuclear disks.",
  "revisions": [
    {
      "version": "v1",
      "updated": "2016-11-20T19:13:59.000Z"
    }
  ],
  "analyses": {
    "keywords": [
      "supermassive black hole binaries",
      "dynamical friction",
      "final hundred-parsec problem",
      "low mass ratio binaries",
      "galaxy black hole mass"
    ],
    "note": {
      "typesetting": "TeX",
      "pages": 17,
      "language": "en",
      "license": "arXiv",
      "status": "editable"
    }
  }
}