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A Keck/DEIMOS Kinematic Study of Andromeda IX: dark matter on the smallest galactic scales

Scott C. Chapman·Rodrigo Ibata·Geraint F. Lewis·Annette M. N. Ferguson·Mike Irwin·Alan McConnachie·Nial Tanvir
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Abstract

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.

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Scott C. Chapman, Rodrigo Ibata, Geraint F. Lewis, Annette M. N. Ferguson, Mike Irwin, Alan McConnachie, Nial Tanvir. 2005-06-06. A Keck/DEIMOS Kinematic Study of Andromeda IX: dark matter on the smallest galactic scales. https://doi.org/10.1086/497686

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