A Keck/DEIMOS spectroscopic survey of faint Galactic satellites: searching for the least massive dwarf galaxies

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[abridged] We present the results of a spectroscopic survey of the recently discovered faint Milky Way satellites Boo, UMaI, UMaII and Wil1.

• Using the DEIMOS spectrograph on Keck, we have obtained samples that contain from 15 to 85 probable members of these satellites for which we derive radial velocities precise to a few km/s down to i~21-22.
• About half of these stars are observed with a high enough S/N to estimate their metallicity to within \pm0.2 dex.
• From this dataset, we show that UMaII is the only object that does not show a clear radial velocity peak.