LEO V: Spectroscopy of a distant and disturbed satellite

M. G. Walker, V. Belokurov, N. W. Evans, M. J. Irwin, M. Mateo, E. W. Olszewski, G. Gilmore

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70 Scopus citations


We present a spectroscopic study of Leo V, a recently discovered satellite of the Milky Way (MW). From stellar spectra obtained with the MMT/Hectochelle spectrograph we identify seven likely members of Leo V. Five cluster near the Leo V center (R < 3′) and have a velocity dispersion of 2.4 +2.4 -1.4 km s-1. The other two likely members lie near each other but far from the center (R 13′ 700 pc) and inflate the global velocity dispersion to 3.7+2.3 -1.4 km s -1. Assuming the five central members are bound, we obtain a dynamical mass of M = 3.3+9.1 -2.5 × 105 M (M/LV = 75+230 -58[M/LV ]). From the stacked spectrum of the five central members we estimate a mean metallicity of [Fe/H]=-2.0 0.2 dex. Thus, with respect to dwarf spheroidals of similar luminosity, Leo V is slightly less massive and slightly more metal rich. Since we resolve the central velocity dispersion only marginally, we do not rule out the possibility that Leo V is a diffuse star cluster devoid of dark matter. The wide separation of its two outer members implies Leo V is losing mass; however, its large distance (D 180 kpc) is difficult to reconcile with MW tidal stripping unless the orbit is very radial.

Original languageEnglish (US)
Pages (from-to)L144-L147
JournalAstrophysical Journal
Issue number2
StatePublished - 2009


  • Dark matter
  • Galaxies: dwarf
  • Galaxies: kinematics and dynamics
  • Local Group

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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