LEO V: Spectroscopy of a distant and disturbed satellite

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

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Abstract

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)
JournalAstrophysical Journal
Volume694
Issue number2
DOIs
Publication statusPublished - 2009

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Keywords

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

ASJC Scopus subject areas

  • Space and Planetary Science
  • Astronomy and Astrophysics

Cite this

Walker, M. G., Belokurov, V., Evans, N. W., Irwin, M. J., Mateo, M., Olszewski, E. W., & Gilmore, G. (2009). LEO V: Spectroscopy of a distant and disturbed satellite. Astrophysical Journal, 694(2). https://doi.org/10.1088/0004-637X/694/2/L144