{
  "id": "2006.01867",
  "version": "v1",
  "published": "2020-06-02T18:32:55.000Z",
  "updated": "2020-06-02T18:32:55.000Z",
  "title": "Repeated mergers and ejection of black holes within nuclear star clusters",
  "authors": [
    "Giacomo Fragione",
    "Joseph Silk"
  ],
  "comment": "15 pages, 10 figures, 1 table",
  "categories": [
    "astro-ph.GA",
    "astro-ph.CO",
    "astro-ph.HE"
  ],
  "abstract": "Current stellar evolution models predict a dearth of black holes (BHs) with masses $\\gtrsim 50$ M$_\\odot$ and $\\lesssim 5$ M$_\\odot$, and intermediate-mass black holes (IMBHs; $\\sim10^2- 10^5$ M$_\\odot$) have not yet been detected beyond any reasonable doubt. A natural way to form massive BHs is through repeated mergers, detectable via gravitational wave emission with current LIGO/Virgo or future LISA and ET observations. Nuclear star clusters (NSCs) have masses and densities high enough to retain most of the merger products, which acquire a recoil kick at the moment of merger. We explore the possibility that IMBHs may be born as a result of repeated mergers in NSCs, and show how their formation pathways depend on the NSC mass and density, and BH spin distribution. We find that BHs in the pair-instability mass gap can be formed and observed by LIGO/Virgo, and show that the typical mass of the ejected massive BHs is $400$--$500$ M$_\\odot$, with velocities of up to a few thousand km s$^{-1}$. Eventually some of these IMBHs can become the seeds of supermassive BHs, observed today in the centers of galaxies. In dwarf galaxies, they could potentially solve the abundance, core-cusp, too-big-to-fail, ultra-faint, and baryon-fraction issues via plausible feedback scenarios.",
  "revisions": [
    {
      "version": "v1",
      "updated": "2020-06-02T18:32:55.000Z"
    }
  ],
  "analyses": {
    "keywords": [
      "nuclear star clusters",
      "black holes",
      "repeated mergers",
      "current stellar evolution models predict",
      "gravitational wave emission"
    ],
    "note": {
      "typesetting": "TeX",
      "pages": 15,
      "language": "en",
      "license": "arXiv",
      "status": "editable"
    }
  }
}