{
  "id": "1608.01327",
  "version": "v1",
  "published": "2016-08-03T20:04:58.000Z",
  "updated": "2016-08-03T20:04:58.000Z",
  "title": "NIHAO XI: Formation of Ultra-Diffuse Galaxies by outflows",
  "authors": [
    "Arianna Di Cintio",
    "Chris B. Brook",
    "Aaron A. Dutton",
    "Andrea V. Macciò",
    "Aura C. Obreja",
    "Avishai Dekel"
  ],
  "comment": "submitted to MNRAS Letter, comments welcome",
  "categories": [
    "astro-ph.GA",
    "astro-ph.CO"
  ],
  "abstract": "We address the origin of Ultra-Diffuse Galaxies (UDGs), which have stellar masses typical of dwarf galaxies but effective radii of Milky Way-sized objects. Their formation mechanism, and whether they are failed $\\rm L_{\\star}$ galaxies or diffuse dwarfs, are challenging issues. Using zoom-in cosmological simulations from the NIHAO project, we show that UDG analogues form naturally in medium-mass haloes due to episodes of gas outflows associated with star formation. The simulated UDGs live in isolated haloes of masses $10^{10-11}\\rm M_{\\odot}$, have stellar masses of $10^{7-8.5}\\rm M_{\\odot}$, effective radii larger than 1 kpc and dark matter cores. They show a broad range of colors, an average S\\'ersic index of 0.83, a typical distribution of halo spin and concentration, and a non-negligible HI gas mass of $10^{7-9}\\rm M_{\\odot}$, which correlates with the extent of the galaxy. Gas availability is crucial to the internal processes that form UDGs: feedback driven gas outflows, and subsequent dark matter and stellar expansion, are the key to reproduce faint, yet unusually extended, galaxies. This scenario implies that UDGs represent a dwarf population of low surface brightness galaxies and should exist in the field. The largest isolated UDGs should contain more HI gas than less extended dwarfs of similar $\\rm M_{\\star}$.",
  "revisions": [
    {
      "version": "v1",
      "updated": "2016-08-03T20:04:58.000Z"
    }
  ],
  "analyses": {
    "keywords": [
      "ultra-diffuse galaxies",
      "nihao xi",
      "feedback driven gas outflows",
      "low surface brightness galaxies",
      "stellar masses"
    ],
    "note": {
      "typesetting": "TeX",
      "pages": 0,
      "language": "en",
      "license": "arXiv",
      "status": "editable"
    }
  }
}