THE OUTER LIMITS OF THE M31 SYSTEM: KINEMATICS OF THE DWARF GALAXY SATELLITES AND XXVIII & AND XXIX

We present Keck/DEIMOS spectroscopy of resolved stars in the M31 satellites And XXVIII and And XXIX. We show that these are likely self-bound galaxies based on 18 and 24 members in And XXVIII and And XXIX, respectively. And XXVIII has a systemic velocity of -331.1 + or - 1.8 km s super(-1) and a velocity dispersion of 4.9 + or - 1.6 km s super(-1), implying a mass-to-light ratio (within r sub(1/2)) of ~44 + or - 41. And XXIX has a systemic velocity of -194.4 + or - 1.5 km s super(-1) and velocity dispersion of 5.7 + or - 1.2 km s super(-1), implying a mass-to-light ratio (within r sub(1/2)) of ~124 + or - 72. The internal kinematics and implied masses of And XXVIII and And XXIX are similar to those of dwarf spheroidals (dSphs) of comparable luminosities, implying that these objects are dark-matter-dominated dwarf galaxies. Despite the large projected distances from their host (380 and 188 kpc), the kinematics of these dSph suggest that they are bound M31 satellites.