{
  "id": "2010.07313",
  "version": "v1",
  "published": "2020-10-14T18:00:04.000Z",
  "updated": "2020-10-14T18:00:04.000Z",
  "title": "Stellar Velocity Dispersion and Dynamical Mass of the Ultra-Diffuse Galaxy NGC 5846_UDG1 from the Keck Cosmic Web Imager",
  "authors": [
    "Duncan A. Forbes",
    "Jonah S. Gannon",
    "Aaron J. Romanowsky",
    "Adebusola Alabi",
    "Jean P. Brodie",
    "Warrick J. Couch",
    "Anna Ferre-Mateu"
  ],
  "comment": "6 pages, 5 figures, MNRAS",
  "categories": [
    "astro-ph.GA",
    "astro-ph.CO"
  ],
  "abstract": "The ultra-diffuse galaxy in the NGC 5846 group (NGC 5846_UDG1) was shown to have a large number of globular cluster (GC) candidates from deep imaging as part of the VEGAS survey. Recently, Muller et al. published a velocity dispersion, based on a dozen of its GCs. Within their quoted uncertainties, the resulting dynamical mass allowed for either a dark matter free or a dark matter dominated galaxy. Here we present spectra from KCWI which reconfirms membership of the NGC 5846 group and reveals a stellar velocity dispersion for UDG1 of $\\sigma_{GC}$ = 17 $\\pm$ 2 km/s. Our dynamical mass, with a reduced uncertainty, indicates a very high contribution of dark matter within the effective radius. We also derive an enclosed mass from the locations and motions of the GCs using the Tracer Mass Estimator, finding a similar mass inferred from our stellar velocity dispersion. We find no evidence that the galaxy is rotating and is thus likely pressure-supported. The number of confirmed GCs, and the total number inferred for the system ($\\sim$45), suggest a total halo mass of $\\sim2 \\times 10^{11}$ M$_{\\odot}$. A cored mass profile is favoured when compared to our dynamical mass. Given its stellar mass of 1.1$\\times$10$^{8}$ M$_{\\odot}$, NGC 5846_UDG1 appears to be an ultra-diffuse galaxy with a dwarf-like stellar mass and an overly massive halo.",
  "revisions": [
    {
      "version": "v1",
      "updated": "2020-10-14T18:00:04.000Z"
    }
  ],
  "analyses": {
    "keywords": [
      "stellar velocity dispersion",
      "keck cosmic web imager",
      "dynamical mass",
      "ultra-diffuse galaxy ngc",
      "dark matter"
    ],
    "note": {
      "typesetting": "TeX",
      "pages": 6,
      "language": "en",
      "license": "arXiv",
      "status": "editable"
    }
  }
}