{
  "id": "1612.01529",
  "version": "v1",
  "published": "2016-12-05T21:00:03.000Z",
  "updated": "2016-12-05T21:00:03.000Z",
  "title": "The tangential velocity excess of the Milky Way satellites",
  "authors": [
    "Marius Cautun",
    "Carlos S. Frenk"
  ],
  "comment": "5 pages, 5 figures, submitted to MNRAS Letters",
  "categories": [
    "astro-ph.GA",
    "astro-ph.CO"
  ],
  "abstract": "We estimate the systemic orbital kinematics of the Milky Way classical satellites and compare them with predictions from the \\Lambda{} cold dark matter (\\Lambda{}CDM) model derived from a semi-analytical galaxy formation model applied to high resolution cosmological N-body simulations. We find that the Galactic satellite system is atypical of \\Lambda{}CDM systems. The subset of 10 Galactic satellites with proper motion measurements has a velocity anisotropy, \\beta=-2.2$\\pm$0.4, that lies in the 2.9% tail of the \\Lambda{}CDM distribution. Individually, the Milky Way satellites have radial velocities that are lower than expected for their proper motions, with 9 out of the 10 having at most 20% of their orbital kinetic energy invested in radial motion. Such extreme values are expected in only 1.5% of \\Lambda{}CDM satellites systems. This tangential motion excess is unrelated to the existence of a Galactic \"disc of satellites\". We present theoretical predictions for larger satellite samples that may become available as more proper motion measurements are obtained.",
  "revisions": [
    {
      "version": "v1",
      "updated": "2016-12-05T21:00:03.000Z"
    }
  ],
  "analyses": {
    "keywords": [
      "milky way satellites",
      "tangential velocity excess",
      "galaxy formation model",
      "proper motion measurements",
      "galactic satellite"
    ],
    "note": {
      "typesetting": "TeX",
      "pages": 5,
      "language": "en",
      "license": "arXiv",
      "status": "editable"
    }
  }
}