{
  "id": "0906.0341",
  "version": "v4",
  "published": "2009-06-01T19:51:41.000Z",
  "updated": "2009-11-30T17:15:10.000Z",
  "title": "A Universal Mass Profile for Dwarf Spheroidal Galaxies?",
  "authors": [
    "Matthew G. Walker",
    "Mario Mateo",
    "Edward W. Olszewski",
    "Jorge Peñarrubia",
    "N. Wyn Evans",
    "Gerard Gilmore"
  ],
  "comment": "Replacement provides corrections to values of half-light radii adopted for eight classical dSphs, including revised tables and figures (conclusions are unchanged). Erratum submitted to ApJ and posted at http://www.ast.cam.ac.uk/~walker/erratum.pdf",
  "journal": "Astrophys.J.704:1274-1287,2009; Erratum-ibid.710:886-890,2010",
  "doi": "10.1088/0004-637X/704/2/1274 10.1088/0004-637X/710/1/886",
  "categories": [
    "astro-ph.CO",
    "astro-ph.GA"
  ],
  "abstract": "(abridged) We apply the Jeans equation to estimate masses for eight of the brightest dSph galaxies. For Fornax we obtain a model-independent constraint on the maximum-circular velocity, Vmax=18_{-3}^{+5} km/s. Although we obtain only lower-limits of Vmax > 10 km/s for the remaining dSphs, we find that in all cases the enclosed mass at the projected half-light radius is well constrained and robust to a wide range of halo models and velocity anisotropies. We derive a simple analytic formula that estimates M(rhalf) accurately with respect to results from the full Jeans analysis. Applying this formula to the entire population of Local Group dSphs, we demonstrate a correlation such that M(rhalf)\\propto rhalf^{1.4\\pm 0.4}, or in terms of the mean density interior to the half-light radius, <rho> \\propto rhalf^{-1.6\\pm 0.4}. This relation is driven by the fact that the dSph data exhibit a correlation between global velocity dispersion and half-light radius. We argue that tidal forces are unlikely to have introduced this relation, but tides may have increased the scatter and/or altered the slope. While the data are well described by mass profiles ranging over a factor of < 2 in normalization (Vmax ~ 10-20 km/s), we consider the hypothesis that all dSphs are embedded within a \"universal\" dark matter halo. We show that in addition to the power law M\\propto r^{1.4}, viable candidates include a cuspy \"NFW\" halo with Vmax ~ 15 km/s and scale radius r_0 ~ 800 pc, as well as a cored halo with Vmax ~ 13 km/s and r_0 ~ 150 pc. Finally, assuming that their measured velocity dispersions accurately reflect their masses, the smallest dSphs now allow us to resolve dSph densities at radii as small as a few tens of pc. At these small scales we find mean densities as large as <\\rho> ~ 5 Msun/pc^3 (200 GeV/cm^3).",
  "revisions": [
    {
      "version": "v4",
      "updated": "2009-11-30T17:15:10.000Z"
    }
  ],
  "analyses": {
    "keywords": [
      "dwarf spheroidal galaxies",
      "universal mass profile",
      "local group dsphs",
      "full jeans analysis",
      "simple analytic formula"
    ],
    "tags": [
      "journal article",
      "famous paper"
    ],
    "publication": {
      "journal": "The Astrophysical Journal",
      "year": 2009,
      "month": "Oct",
      "volume": 704,
      "number": 2,
      "pages": 1274
    },
    "note": {
      "typesetting": "TeX",
      "pages": 0,
      "language": "en",
      "license": "arXiv",
      "status": "editable",
      "inspire": 821874,
      "adsabs": "2009ApJ...704.1274W"
    }
  }
}