2009/02/17 by Matthew G. Walker, M. G. Walker, Vasily Belokurov +11 · 8 citations
Physics and Astronomy · #Astronomy and Astrophysical Research #Scientific Research and Discoveries #Stellar, planetary, and galactic studies #astro-ph.CO #astro-ph.GA
paper · pdf · doi:10.1088/0004-637x/694/2/l144
Accepted for publication in The Astrophysical Journal Letters
arxiv created 2009/02/17 · openalex publication_date 2009/03/13 · arxiv updated 2009/12/01 · openalex created_date 2016/06/24 · openalex updated_date 2026/07/31
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 × 10 5 M ☉ ( M / L V = 75 +230 −58 [ M / L V ] ☉ ). 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.