A Keck/DEIMOS Kinematic Study of Andromeda IX: dark matter on the smallest galactic scales
Chapman, Scott C.
Lewis, Geraint F.
Ferguson, Annette M. N.
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We present the results of a kinematic survey of the dwarf spheroidal satellite of M31, And-IX, which appears to be the lowest surface brightness and also the faintest galaxy (M_V = -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 sigma_v = 6.8+3.0-2.0km/s, which coupled with the low luminosity implies a very high mass to V-band light ratio, M/L ~ 93+120-50msun/lsun (M/L > 17msun/lsun at 99% confidence). Unless strong tidal forces have perturbed this system, this smallest of galaxies is a highly dark matter dominated system.
Chapman, Scott C., Rodrigo Ibata, Geraint F. Lewis, Annette M. N. Ferguson, et al. 2005. "A Keck/DEIMOS Kinematic Study of Andromeda IX: dark matter on the smallest galactic scales." The Astrophysical Journal 632(2): 87-L90