A Keck/DEIMOS Kinematic Study of Andromeda IX: dark matter on the smallest galactic scales
نویسندگان
چکیده
We present the results of a kinematic survey of the dwarf spheroidal satellite of M31, Andromeda IX, which appears to be the lowest surface brightness and also the faintest galaxy (MV = −8.3) found to date. Using Keck/DEIMOS spectroscopic data, we have measured its velocity relative to M31, its velocity dispersion, and its metallicity. It exhibits a significant velocity dispersion σv = 6.8 +3.0 −2.0 km s , which coupled with the low luminosity implies a very high mass to V -band light ratio, M/L ∼ 93 −50 M⊙/L⊙ (M/L > 17M⊙/L⊙ at 99% confidence). Unless strong tidal forces have perturbed this system, this smallest of galaxies is a highly dark matter dominated system. Subject headings: galaxies: dwarf — galaxies: individual (Andromeda V) — galaxies: individual (Andromeda IX) — galaxies: evolution — Local Group
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